When you first start to knit or crochet you can come across many unfamiliar terms. One of the most confusing an be "ply" or "weight". These terms both refer to the thickness of your yarn strand. Traditionally ply described the number of threads used to make up the yarn strand. So if you unwound the end of a 4 ply strand you would have 4 threads, and there would be 8 threads in and 8 ply yarn. Ply is a term used often in NZ and Australia.
This is where weight comes in. Modern manufacturing processes permit yarn to be made using differing techniques and fibres, resulting in different thicknesses with many or few threads to a strand.
2 ply and 3 ply also called lace weight.For a superfine garment, in stocking stitch you would use a 2.00mm knitting needles, but this yarn is more commonly used to make lovely lace pieces like shawls. Lace can be knit on almost any size needle and give a truly wonderful finish. Patterns for this yarn weight an be quite challenging and are not always for the fain hearted.
4 ply and 5 ply also called sock yarn, baby yarn. The construction of these yarns is a little different. Sock yarn often contains a little nylon to give a sock additional structure. This is often used to make fabulous shawls or hats, and the dyes are often random colours. Self striping yarns will knit up as stripes or fair isle. Baby wool is often machine washable, and soft enough of course, for a baby. And then there are other 4 ply yarns, whih might be suitable for socks or babies, but also make very nice clothing. Usually 3.00mm to 3.75mm knitting needles are used for these yarns.
8 ply, double knit (DK). 3.75 - 4.00 are the needles you would expect to use for this commonly used yarn. Almost anything can be made using 8ply., from hats and handbags, to thick socks, coats and jumpers. Lace cables and stocking stitch will all give a good result.
10 ply and 12 ply, aran, worsted, chunky. There is a wide range of lovely patterns available which use 5.50mm needles. This yarn weight is becoming more popular even in warmer climates now, for smaller, stylish accessories with a unique touch.
14 ply to 20 ply, chunky or superchunky. Using 7.00 mm needles, and upwards, there are even chunky yarns suitable for arm knitting. These are worth trying if you are looking for a little extra challenge.