نحيل/شاحب

"thin" I would say in an unattractive word, whereas "slim" is attractive. "She is very slim" and "She has a slim figure" are both compliments. For attractive words, I can't think of too many: slim, in good shape, lean (this is more for describing guys though) Unattractive words: skinny, bony, lanky

Thin : In an attractive way: أَهْيَف - رَشِيق - رَهِيف - مَمْشُوق - مُرْهَف - مُهَفْهَف.. In an unattractive way : ضَامِر - ضَعِيف - مَهْزُول - نَحِيل - خَائِر - هَزِيل..

In a good way: стройная Otherwise: худая, тощая