sometimes called 2 ply it is thin yarn which produces a thin fabric and is used for knitting lace (among other things)
It's more properly called laceweight yarn. It's a very fine yarn, about one or two ply.
Depends on the material of the yarn, diameter, etc.
Your question doesn't make sense. For example: 4-ply yarn is 4 singles plied (twisted and set) together.Lace weight yarn is usually single or 2-ply.
Your answer depends on the yarn weight you're working with. You'll need a longer needle for bulky weight yarn than you will need for lace weight.
Gossamer is a word that means light weight and airy, such as lace. It is also the name of a type of yarn produced by the Knit Picks yarn company, which is a fine, light weight, single strand yarn. There is also a knitting store in Oregon called Gossamer, The Knitting Place. To answer your question, yes, a gossamer shawl would be a shawl that is knitted out of a lace weight, single ply yarn.
For hand embroidery, you might be able to use a lace weight or other thread-weight yarn.
Using Zephyr 2/18 as an example, I would estimate 500 yards.
It depends on the size and style of jumper you want, the stitch pattern being used, and the weight of yarn you have. A large sweater with a dense stitch pattern (such as lots of cables) will require more yarn than a small sweater with a lace pattern. You can knit further with a finer weight of yarn (say a sport weight instead of a worsted weight).
It really depends on the weight of yarn, 32 oz of worsted weight is different then 32 oz of lace weight. Most bands will have the yardage/meterage on them, if you are still not sure, use a knitty noddy or a yarn swift to measure out the yarn, make sure if you are using one of these tools that you know the measurement of the device that you are using. Knitty noddy's are usually a set meterage/yardage, where as a yarn swift can be adjusted to what ever width you would like.
Bernat Satin is medium (or worsted) weight. It can also be classified as a 4 on a scale of 0 to 6, 0 being lace weight and 6 being super bulky weight. Hope that helps. :-)
I think you are asking about Sport weight yarn. Yarn can be divided into "weights" which refer to the diameter of the yarn. Yarn Council of America is attempting to standardize this system of weights (which really doesn't have to do with the actual ounces, pounds, grams or kilograms). Therefore, a Sport-weight yarn would be one that could be called "Fine" (vs a lace or superbulky yarn), or #2-sized yarn or that it generally has 23-26 stitches per 4 inches (a standard gauge length and height), horizontally. You can find more information by following the link I have attached to this answer.
It will depend on the type of yarn. 225 yards of worsted weight yarn is about 100g, but 225 yards of sock weight yarn is about 25g. What is the yarn type?
In the UK, worsted weight yarn corresponds to 10ply (i.e. heavy DK or light aran yarn)