Acid: it belongs to juxtaposition in structure, so it can be understood separately without affecting the overall meaning, that is, "acid" and "astringent" Acid: here is an adjective, feeling weak only because of slight pain caused by fatigue or illness; Astringent: It is also an adjective, and here it means: feeling numb and dry, dull or not smooth. The whole word means that the inner depression and exhaustion make people feel numb and wronged.

Synonym of acid: acid.

Sometimes it's a little bitter, bitter.