I would imagine that not too many people have a favorite yarn size. I actually have one, and it's 70/1 cotton.
Technically, this number means one ply (the “/1”) of size 70 NE cotton yarn. NE refers to Number English and the number is determined by how many 1 yard hanks in this size, times 840 equals 1 pound. So, 1 lb = 70 one-yard lengths of this particular yarn size x 840. The finer the yarn, the higher the count, because it would take more fine yarns x 840 to equal a pound. So random, I know.
Commercially, this number is in between two other common cotton yarn sizes: 60’s, typically used for lawns, broadcloth and other light weight shirtings, and 80’s, used for even finer lawns and voile. It’s not a 2 ply, which would feel slightly more compact and dense. Anyway, the equivalent weight in a 2 ply would be 140/2 which is not super common.
Aesthetically, woven fabric using 70/1 feels just amazing. It’s that perfect weight, finer than a 60's shirting, but not as sheer and light as an 80’s voile. It has a great soft handfeel and drape.
Of course, handfeel and drape are also determined by the yarn count in a particular fabric. But in a poplin stripe construction, for example 220 x 90 (number of yarns in warp x number of weft per square inch), this handfeel is silky and luxurious.
This post can only make sense if you could touch what I’m talking about! If you’re interested, send me a message at hello@scissorsandthings and I’ll see if I can send you a swatch.