I was in Next. (I thought about pretending here that I was shopping somewhere fancier, but it is the only the place in the UK where I've found a pair of trousers that (AmE) fit/(BrE) fitted in the past three years, so they deserve some credit.) On the tag of the ill-shaped trousers/pants was the line Next Woman. That is to say, the item was from their women's range.
Compare this to American brands, where Woman often means 'extra large'. For instance Amazon.com lists 'Woman Sizes' as (US) 14-24. (American 14 = UK 16/18.) The Women's department in an American department store, such as Macy's, will carry precisely those larger sizes. Of course, this is confusing, since there are plenty of women who don't wear these sizes. But it works in the US because there are two other types of departments for smaller women. The Misses department carries the even-numbered sizes 14 and down, and the Juniors department carries odd-numbered sizes (up to 13) that are cut for younger women--or teenagers (smaller bust and hips). The word Misses is seen less these days in the actual marketing of clothing than it was when I was young, but the term is still used to designate sizes. Some non-department store retailers, like J.Jill, make the Misses'/Women's distinction. (There are also Petites in both AmE and BrE, but this category has to do with height, rather than width. One can find Petite Misses and Petite Women's sizes.)
The less-confusing name for women's sizes is (orig. AmE) plus sizes, but one sees the effect of the 'women' designation sometimes in plus sizes, which can be designated as 14W-24W. As Wikipedia (today, at least) explains, the W indicates a difference in cut:
As more and more retailers are rushing to join the plus-size clothing market, the fastest growing sector of the apparel industry, confusion has entered for the consumer regarding sizing. Some lines offering traditional "Misses" sizing have extended their size ranges up to 18 or 20, overlapping the "plus" or "women's" size range. However there is a difference between a Misses size 14 and a Women's size 14W. Traditional plus or "women's" sizing is cut with a deeper arm hole, lower and larger bust-line, and larger waist compared to hip ratio than "Misses" sizes. This results in 14W being about one size larger than a Misses Size 14. This cut difference also means a better fit for differing body types. Those women with a traditional hour glass or pear body type will usually find a Misses size range fits better. Women who have a rounder, more apple shaped figure and carry their weight mainly in the bust and abdomen, will find the traditional plus-size clothing or Women's Sizes will fit their figures better.Of course, the fact that the US has invented this vocabulary for large clothing might be taken to corroborate the picture of Americans as fat--and it's true that Americans on average are fatter than other nationalities. But it's worth pointing out that the UK is not far behind--if at all behind. According to WrongDiagnosis.com, the rate of obesity (as opposed to mere over-weight) is 14.6% in both countries. However, as this site points out, attitudes toward(s) obesity vary in the two countries.