There are many ways to knit a sweater. In addition to the many technical aspects of knitting (flat, round, bottom-up, top-down or sleeve to sleeve), there are also different types of construction to form the shoulders and sleeves.
You will find here some explanations and diagrams to understand and recognize the most common styles such as the "yoke", the "raglan", the "set-in sleeve" or the "drop shoulder".
INTRODUCTION
The technical aspects include several ways to knit a sweater. Since the objective of this article is to present the different styles of sweaters, I will not dwell too much on the technical details but it is necessary to understand the basics.
WORK FLAT : This method involves knitting with straight needles and in rows back and forth each piece separately: the front, the back and the sleeves. Then the pieces are sewn together: normally the shoulders of the back and front are joined together, then the sides of the body and the bottom of the sleeve are sewn together. This is a very common method as it was practically the only one before the invention of circular needles!
WORK IN THE ROUND: As the name suggests, this method means that the sweater is knitted in the round on a circular needle. With this method, we avoid the assembly (sewing) of the individual pieces that many knitting enthusiasts hate.
THAT'S NOT ALL! IN ADDITION TO HAVING THE CHOICE OF KNITTING FLAT OR IN THE ROUND, WE HAVE ONE MORE CHOICE TO MAKE:
BOTTOM-UP: When knitting a sweater from the bottom up, you start by knitting the bottom of the body (usually the ribs) and then work your way up, row by row (or round by round) to the underarms. It is at this point that you need to create the holes for the sleeves and the next steps will depend on the style of sweater you are knitting.
TOP-DOWN: When knitting a sweater from top to bottom, you start by knitting the neckline. Then the formation of the shoulders and armholes will depend on the style of sweater you are knitting.
DIFFERENT STYLES OF KNITTED SWEATERS
KNITTING A "DROP SHOULDER" SWEATER
The "Drop shoulder" style sweater is the simplest: the back and front are shaped square (or rectangular for a longer sweater) and the sleeves are grafted directly on each side of the shoulders.
The "Drop Shoulder" sweater is more often knitted flat, in pieces that are assembled later. For those who wish to avoid seams, it is possible to knit the lower part of the body and sleeves in the round but the upper part of the body and sleeves will still have to be knitted flat and a seam will be required to finish the sweater.
KNITTING A "SET-IN SLEEVE" SWEATER
This sweater is very similar to the "Drop shoulder" with the difference that the sleeves are embedded in the body: stitches are binded-off and/or decreased in the upper part of the body, on each side of the back and the front to insert the sleeves.
KNITTING A RAGLAN SWEATER
The raglan sweater is a style that features a sleeve that runs diagonally up from the armpits to the neckline. The raglan sweater can be knit flat or in the round from start to finish, from the bottom up or top down!
Here's what the raglan sweater looks like from above (if you knit it in the round, from top to bottom, that's exactly what your knitting will look like)
The central elipse represents the neck hole, the blue diagonal lines represent the increases (if knitting from the top down) or decreases (if knitting bottom up). The increases (or decreases) are always done at the same place, about every other row (or turn).
KNITTING A YOKE SWEATER
Like the raglan, the pull yoke is knitted entirely in the round and can be made from the bottom up or from the top down. Unlike the raglan, the increases (or decreases) are spread over just a few rounds around the bust.
This is what the yoke sweater looks like from above (if you knit the yoke from the top down, this is what your knitting will look like):
The blue ellipses represent increases (if knitting from top to bottom) or decreases (if knitting from bottom to top). Unlike the raglan, the increases are not made every other round, but are spread over more or less 5 rounds.
EN CONCLUSION
There are many ways to knit a sweater and this presentation is only a summary of the most common methods. If you are interested in the subject, I suggest the following rbooks: Step-by-Step Instructions for 13 Classic Sweaters by Maggie Righetti and The Beginner's Guide to Writing Knitting Patterns: Learn to Write Patterns Others Can Knit de Kate Atherley