Armscye
The armscye or armhole is the opening in the bodice where you attach the sleeve.
 
Seam allowance
The extra fabric added to the pattern pieces to allow for seams.
 
Backstitch
2 or 3 reverse stitches to secure the stitches at the beginning and end of a seam. A backstitch (or a back tack )will secure the stitches and prevent your seam from coming undone. 

Bar tack
a small row, of narrow zig-zag stitches to reinforce or keep a facing in place. They are used on a jeans fly, jeans belt loops, and buttonholes.

Basting
Temporary stitches to hold something in place. You can do it by hand or by sewing machine. 

Bias
Bias refers to the diagonal direction of a piece of fabric, drawn at an exact 45-degree angle to the selvage or grain line. Woven fabric has the greatest amount of stretch in this direction even when it is a non-stretch fabric.

Bias binding
Strips of fabric cut on a 45-degree angle to the selvage. In this direction, the fabric is stretchy and it adjusts well to curves, making it a great finish for necklines, (curved) hems or armholes. The strip is used to encase the raw edge of a hem or a seam. By using a contrasting or a piece of patterned fabric you can add a pop of colour to the inside of a garment.
 
Bound seams
With bound seams, you use double-fold bias binding to finish the raw edge of the seam allowance after it’s pressed open or to one side binding seam allowances together as one. This is a lovely technique but it adds a bit of bulk to your seam allowance. The Hong Kong seam creates a less bulky seam.
This finish is an elegant way to finish unlined jackets or coats.

Button band/button stand
A button band or button stand always consists of two panels, one side holds the buttons and the other side has buttonholes. The button band is either a separate piece of fabric or an extension of the panel it’s attached to.

Buttonhole
A reinforced hole in the fabric slightly bigger than the button that needs to pass through it. Most sewing machines have a buttonhole foot and can make a beautiful buttonhole in 4 steps. Or you can make them using a zig-zag stitch on a sewing machine, or by hand using a blanket stitch.

Whatever the project is, always make a few test buttonholes to see if you need heavier fusible interfacing to get a good result. Making a test buttonhole is also a good way to see how the colour thread you chose looks with your main fabric and to check if your button easily passes through the hole.

You need to make the buttonholes and open them up first before you place the buttons. Line up the edges of the two button stands, and poke a marking pen through the buttonholes to mark the button placement. It’s easy and you will always have the buttons line up perfectly with the buttonholes.

Calico
A woven fabric from unbleached cotton. The fabric often has little brown specks in it from the husk of the cotton plant. It’s a fairly cheap fabric making it very suitable to test the fit of a garment. 

Clip / notch
Clipping and notching will give you better results in convex (scalloped hem) and concave (neckline) curves. A clip is a snip towards the stitching and a notch is a v-shaped (wedge) cut out towards the stitching. To get the best result, cut close to the stitch line but not through.

Notch 
A notch can also mean a marking on the pattern to help align two pieces on a long seam or curved pattern pieces.

Cut on fold
When a pattern tells you that you need to cut a pattern piece on fold, it means you need to align that edge to the fabric fold. That way you only have to cut out half of the pattern piece (don’t cut the fold!), but when you unfold the fabric you have a full symmetrical piece of your garment. This is often the case for a bodice front without a centre seam or a bodice back without a centreback seam.

Darts
Darts are used to shape the garment around the waist, bust, shoulders, and sometimes sleeves. They are often shaped like triangles or diamonds.
 
Double-fold hem
A hem that’s folded towards the inside of the garment, for the first fold you fold the raw edge toward the wrong side of the fabric, and then a second fold again towards the inside of the garment encasing the raw edge.

Ease / wearing ease / design ease / negative ease
Ease is the room in the garment that allows you to move and sit. Patterns are all designed with different amounts of ease.

In short, a pattern is made up of:
Body measurements + wearing ease + design ease

A minimum or wearing ease is around:
5cm / 2” around the bust
2.5 cm / 1″ around the waist
3.8 cm / 1 1/2″ around the hips
And on top of wearing ease, design ease is added. There are no rules, it’s up to the designer or your personal preference.
 
Negative ease
Negative ease is used in knit garments. Negative ease is when you end up with a garment that is smaller than your body measurements, but the stretch in the fabric will provide ease and room for movement.

Easing in
When one of two pattern pieces, that need to fit together, has extra fabric you need to ease in. For example, sleeve caps often have extra fabric than needs to be eased in. You can gather the extra fabric slightly, but without creating pleats, to distribute the extra fabric evenly before you set in the sleeve. Or you can use a technique called crimping.

Crimping is when you sew a line of stitches, just inside the seam allowance, next to the stitch line, in the pattern piece that needs to be eased in, and you force more fabric into those stitches. While sewing you put your finger just behind the presser foot, letting the fabric bulk up between your finger and the presser foot. This way the fabric is slightly gathered but in a very even manner. Leave the gathers intact until you start pinning.

Feed dogs are another tool to help you get a good result when you are setting in sleeves. Unless you have a walking foot, the feed dogs will always pull the lower fabric through the machine a little bit faster than the top fabric and you can use this to your advantage when you are setting in sleeves or easing in fabric, by always sewing with the larger piece on the bottom, against the feed dogs.

Edgestitch
A line of stitches close to the edge of a seam, hem, or pocket opening. often only a needle width away (0.15 cm / 1/16″) from the edge.  

Feed dogs
The feed dogs are the teeth that transport the fabric through your sewing machine. They are located under the presser foot and can be dropped when you are sewing buttons on your sewing machine.

Finger press
When you use your fingers, fingernail, or another flat and smooth object to flatten or open a seam.

French seams
French seams are a great way to finish your fabric if you don’t have a serger because the French seam encases the raw edge of your fabric.

The technique is mostly used on straight seams, but with a bit of practice, the technique works well on curved seams. If you venture into curved seams, I suggest you keep the seam allowance narrow, because wider seams will pucker easily. 

Facing
Facing is a way to finish the raw fabric edges, stabilize, add structure, and strength. They are a partial lining often made from the main fabric and are used on necklines and armholes. 

Facing can be a separate panel or cut-on facing. Cut on facings are part of the panel they are facing. Cut on facings are often used in a waterfall neckline or a button band. Facings are often used in combination with interfacing

Foldline
The line on a pattern where the fabric should be folded.

Fusible interfacing
Fusible interfacing can be permanently fused with the wrong side of the fabric to add strength and structure to your garment. It’s often used in button bands, buttonhole areas, welt pockets, collars, cuffs but it can also be used in entire panels.

One side has a glue on it that will fuse with the fabric, you should be able to feel small bumps where the glue is. The fusible interfacing is fused by applying heat and pressure for a certain amount of time, this depends on the type you bought.

Always use a pressing cloth to apply the fusible interfacing to avoid the glue fusing with your iron. After applying the fusible interfacing let it cool down before you move the piece you’ve just fused.

There are many different kinds and weights that you can and should use depending on your project and fabric. Some is awful and papery and won’t even hold well so always try to buy the interfqcing that feels most like fabric.

Fusible interfacing relatively easy to use, but for tailored garments like jackets and heavily textured fabrics you often see sew-in interfacing sometimes in combination with fusible interfacing.

Gather
Gathered fabric is used to create fullness or ruffles. You sew one or two lines of gathering stitches just inside and/or outside the stitch line.

Use a long stitch length (5mm and up) on your sewing machine and stitch well within the seam allowance. Some patterns ask for 2 or more gathering lines but as long as you use good, strong thread you should not need this. 
Don’t back stitch when you start stitching and leave long thread tails. Anchor the thread tails on one side around a pin, and carefully hold the loose (top or bottom) thread tails and slide the fabric you want to gather along the thread.

Grade
Cut seam allowances in graduated widths to eliminate bulk and prevent a ridge from showing on the right side of the garment. Trim the top layer to 0.3cm / 1/8″ and the bottom layer to 0.6cm / 1/4″and interfacing close to the stitching. 

Grading is also the process of going between sizes on a pattern to adjust the pattern to fit you, as well as the process a pattern designer goes through to create different sizes for each pattern. 

Grain / Cross grain
Grain describes the direction of the warp and weft of a woven fabric.
The grain or lengthwise grain of the fabric runs parallel to the selvage. This direction has little to no stretch.
The cross-grain runs perpendicular to the selvage. This direction has a little stretch or give.

Grainline
The long line with an arrow printed on the pattern. Most of the time this line should be placed parallel to the lengthwise grain / selvage / the length of the fabric. This is also referred to as, on-grain and straight of grain. 

In general, always place pattern pieces on-grain and in the same direction, because if the fabric has a nap (velour, velvet, fake fur, corduroy, etc.) you will see that they seem to have a different colour or shade in when light hits the fabric.

In some cases, you can also use the crosswise grain. For example; if you want to create a fun design detail with striped fabrics, and play with the direction of the print on a yoke or a cuff.

Another time to experiment with lengthwise vs crosswise grain placement is when you don’t have enough fabric and need to get creative with your yardage. However be this can affect how the garment hangs of your body (hello twisting pant leg), so do this with caution.

Hong Kong seam
Hong Kong seams or a Hong Kong finish use a strip of bias-cut fabric to encase the raw edge of your fabric, but the binding on the wrong side of the seam allowance is left raw so it’s less bulky than bound seams.

Hem 
The bottom edge of a garment often folded up towards the inside of the garment.

Interfacing
An additional layer of fabric that is used to stabilize, add structure, “crispness” and strength. It lays between the lining/facing and the outer fabric of a garment.

Interlining
A layer used to add warmth to your garment. It sits between the outer fabric and the lining.

Invisible zip
A zip which has the teeth on the inside, and just the pull on the outside. This zip is sewn with a special presser foot and seams. when it’s done right it’s hard to see the zipper in the seam, hence the name.

Knit fabric/knits
Knit fabric is a very stretchy material and it’s made by a series of interlocking loops. Knit fabrics are made in the same way as that scarf you tried to knit for your doll when you were seven, but much finer threads and needles 😉

Lining
A layer of fabric on the inside of a garment to hide construction seams and details, add warmth and make it more comfortable to wear and easier to put on.

Mark
Transferring pattern symbols and markings to fabric. There are many ways to do this.
Using erasable pens – by far the cheapest, most accurate way to mark and you can buy the pens everywhere now (Pilot Frixion are good)
Using dressmakers carbon paper and a tracing wheel 
Tailors tacks are made with thread
Chalk
Water-soluble fabric markers
Pins
A small clip in the seam allowance. I like to cut out tiny triangles. I make an angled cut (max. 0.5 cm / a scant 1/4”) and then make another angled cut, cutting out a small triangle.
 
Muslin/ toile
Light and loosely woven cotton fabric, undyed and often used to make test garments. 

Also a test garment or toile, made out of muslin fabric, unbleached cotton or simply a cheaper fabric. Sometimes sewers talk about a wearable muslin, this is when you make a test garment in a cheaper but nice fabric and keep your fingers crossed it turns out nice enough to wear.

Notch / Clip 
Clipping and notching will give you better results in convex (scalloped hem) and concave (neckline) curves. A clip is a snip towards the stitching and a notch is a v-shaped (wedge) cut out towards the stitching. To get the best result, cut close to the stitch line but not through.

A notch is also a marking on the pattern to help align two pieces. You will get single botches on pattern pieces where two front pieces join each other, or a front and back piece join, and two notches on back pieces that join each other. Some designers use 3 notches for this.

Notions
When a pattern calls for notions it’s items like buttons, zippers, hooks, lace, elastic, etc. All the small accessories you need to finish your garment.

Pins
There are many different pins. They can vary in length and thickness, with ball-shaped glass heads for ironing over and ones completely without heads – a nightmare in my opinion as not easy to remove when sewing and they often end up inside the machine and can cause untold damage inside. 

Placket
A partial button band/button closure. You see these plackets in sleeve cuffs, polo shirts, and pop over shirts and anoraks.
 
Pleat
A fold of fabric that is stitched down to create fullness or shape.
 
Pressing
Use an iron to press seams open or to one side. Do this while you work on your garment to get the best results. This is different than ironing the fabric, so lift the iron slightly when you move then press down.

Don’t over press! Your fabric may become shiny or the seam allowance will cause ridges on the outside of your garment. 

Take extra care when working with woolens. apply minimal pressure with your steam iron, just enough to open the seams, then give it a final burst of steam, remove the iron and (once the heat is bearable) use the pressure from your hand to hold the seam open and let it cool. If you love sewing with wool, consider investing in a wooden clapper to set woollen seams.

When a fabric has a lot of texture, you can also use a thick towel on top of your ironing board.
 
Pressing cloth
A piece of fabric to protect your fabric when pressing. You hold it between the iron and your project or garment, if you don’t have a steam iron you can dampen the pressing cloth for better results. I just use a piece of white or unbleached cotton. 

Why use a pressing cloth? A pressing cloth will help prevent shine on your fabric and markings from your iron and it will protect your iron when you are using fusible interfacing. 

Presser foot
Official name for the foot of the sewing machine, which holds the fabric and helps feed it through. You can change your foot to help insert zips, make quilts, darn, bind your edges etc.

Raw edge
The unfinished, ripped or cut edge of the fabric.

Right side / Wrong side
The right side of the fabric or the face of the fabric is the side you see on the outside of the garment.
The wrong side is the backside of a fabric and the inside of the garment. Sometimes they look the same; in that case, pick a side and stick with it.

Running stitch
A simple hand-sewn stitch that weaves up and down through the fabric, creating a dashed line of stitches. Use this for basting or gathering fabric.

Seam
The line where you sew together two pieces of fabric. 

Seam allowance
The fabric between the edge of the fabric and the stitch line. The width can vary between pattern companies and in a garment. Always check the pattern descriptions and pattern pieces.

Some commonly used seam allowances are:
0.6 cm / 1/4″
1 cm / 3/8″
1.6 cm / 5/8″
2.5 cm / 1″
Narrow seam allowances are great used on curves and for special seam finishes, like a French seam. Wider seam allowances can also be used for certain special finishes like French seams on heavier fabrics, flat-felled seams, or when you might want to adjust the fit.

Seam finish
This can be done in many different ways and it’s handy to learn a few different techniques. A seam finish prevents the raw edge of your seam from fraying. You can overlock the edges, zigzag them, or simply use pinking shears.  Other options include French seams, bound edges, Hong Kong seams.

Seam ripper
A small tool to unpick a row of stitches. Replace these occasionally when the knife is dull.

Overlocker
A specialized type of sewing machine that can trim and overlock raw edges all in one go. It has 3, 4, or 5 needles and creates a stretchy seam finish, making it very suitable for knits.

Sew-in interfacing
Sew-in interfacing is sewn in by hand and is mostly used in structured and tailored garments like jackets. 

Stay stitch
A line of stitches to stabilize the fabric before it’s sewn into a garment. The stitches should be just inside the seam allowance, very close to the final stitch line.
Where to use stay-stitching? Stay stitches are mostly used around bias-cut seams, armhole curves, necklines, or even crotch seams to prevent it from stretching out of shape. These are all places where fabric easily stretches. So, while you are handling your cut out fabric pieces, moving them to and from the sewing machine, turning your partly sewn garment inside out for sewing or pressing there is a chance of these curves distorting and stretching. A stay stitch will help prevent this.

Straight stitch
The most basic machine stitch, that produces a single row of straight, even stitches. It’s used to construct a garment and for topstitching.
 
Stitch length
Length of a stitch. The length will depend on your fabric, project, and the purpose. 

For clothing construction, 2.5 mm is a good starting point. When you are working with thicker fabrics or 3 mm is a good starting point. For topstitching a longer stitch length of 3 mm / 3,5 mm often looks better.  Always do a little test to see if you like how it looks.

Tailor’s tacks
Loose hand sewed stitches to transfer pattern markings on to the fabric.

Tailor’s ham or dressmaker’s ham
A firm cushion for pressing. It’s used to shape collars, sleeves, darts, and curves.

Thread Tension
Thread tension on a sewing machine is controlled in two spots:

Top – Where the top thread travels through the tension discs, they are at the top of your sewing machine.
Bottom – In the bobbin case.
The top tension can be easily adjusted, often with a dial on the sewing machine. This needs to be adjusted for buttonholes and for thicker and thinner fabrics.

The bottom tension can also be adjusted, by turning the small screw on your bobbin case…but this is rarely done or necessary if you are working with regular all-purpose sewing threads. But if you are using thicker or thinner threads in your bobbin, you need to adjust your bobbin tension. And sometimes after a few years of use, the screw on your bobbin tightens or loosens itself.

Many of us are told never to touch the screw on the bobbin, but if it needs adjusting…it needs adjusting. I find it helpful to think of the screw as a clock and only turn 10 or 15 minutes at a time. And a good way to remember which way to turn, lefty loosy and righty tighty.

Toile/ muslin
The French word toile can refer to canvas or linen but is often used to describe a test garment or muslin

Topstitch
topstitching is a line of stitches on the outside of a garment. Topstitching can be used for different purposes:

Decorative, like on back pockets on jeans.
Added strength.
Help to flatten a seam, like an inseam on jeans.
Secure facings, pockets
 
Trim
Cut a seam allowance to a narrower width. This will eliminate bulk and help with curved seams.

Twin Needle / Double Needle
Twin needles feature two needles and it sews two rows of parallel stitches simultaneously. They can be used to do topstitching on seams or to hem T-shirts.

Under stitch 
Helps to keep facings (lining or bias binding) in place and prevent them from peeping out on the outside of your garment. Press seam allowance towards the facing. Stitch both seam allowances and the facing close to the seam line on the facing. Press your facing to the inside.

Underlining
An extra layer of fabric cut as a duplicate of a section in a garment. When the garment is sewn, there two pieces are treated as one. Underlining is used with sheer fabrics adding an opaque backing. It can also serve as a backing for an unstable fabric.

Woven fabric
Woven fabrics are made by weaving together many threads. There are lengthwise threads (warp) and crosswise threads (weft). The most basic weave is a plain weave; where each weft thread travels through the warp threads by going over one, then under the next, and so on. Then on the next pass, it will repeat the same pattern but alternate threads, producing a checkered surface.
Woven don’t stretch unless they are used on the bias or an elastic is woven into the fabric, like elastane.

Walking foot
A presser for that helps feed multiple layers of fabric through your sewing machine more evenly. A walking foot is often used by quilters because it helps to evenly transport the layers trough the sewing machine.

Wrong side
The back of the fabric and usually the inside of the garment. If it’s hard to see which side is the right or wrong side of your fabric, use pins or chalk to mark the fabric.
If you have trouble seeing the backside of your knit fabric, remember that the raw edges tend to curl towards the right side of the fabric.

Zigzag stitch
Z-shaped stitch that can be used on knits, stretch fabrics, to sew buttonholes and as a finish for raw edges.
 
Zip Foot
When attaching any zipper, you need to sew close to the edge of the zipper teeth and a zipper foot will help you do just that. A zipper foot can be snapped onto the left or right of the sewing foot ankle, as needed