Slimmer most often means “more slim” — thinner than before, or thinner than someone else. That is just slim with -er.

Slimmer「slimmer」 most often means最常見的意思是 'more slim'「更瘦」 — thinner than before, or thinner than someone else比以前更瘦，或是比別人更瘦。That那 is just slim with -er就是slim加上-er而已。

In British English, though, a slimmer is also a person who is trying to get thinner by eating less and moving more. Magazines and clubs have long talked about “slimmers” in that way.

In British English, though不過在英式英文裡, a slimmer is alsoslimmer也可以指 a person who is trying to get thinner正在努力想變瘦的人, by eating less and moving more靠少吃多動的方式。Magazines and clubs雜誌和社團 have long talked about很早就這樣提到 'slimmers' in that way「slimmers」這個字了。

American English usually does not use the noun like that; people say someone is on a diet or trying to lose weight.

American English usually does not use the noun like that美式英文通常不會這樣用這個名詞; people say而是會說 someone is on a diet or trying to lose weight某人is on a diet（在節食）或trying to lose weight（想減重）。

The verb behind the British noun is to slim: to make yourself thinner. You have to hear the sentence to know which slimmer you have: “a slimmer dress” (more slim) is not “a slimmer” (a person).

The verb behind the British noun這個英式名詞背後的動詞 is to slim就是to slim: to make yourself thinner意思是讓自己變瘦。You have to hear the sentence你得聽整句話 to know which slimmer you have才知道遇到的是哪一個slimmer: 'a slimmer dress' (more slim)「a slimmer dress」（更瘦的洋裝） is not不是 'a slimmer' (a person)「a slimmer」（指人）。