酸suān sour, tart, acidic (taste) acid (chemistry) to feel sore, to ache jealous, envious, sarcastic, bitter, cynical (informal) HSK 4TOCFL 4
過去guòqù past, former times, bygone days to pass, to go by (of time) in the past, previously, formerly to go over HSK 2TOCFL 4
奇怪qíguài strange, weird, odd, peculiar to find strange, to wonder about Tends to have a negative connotation. HSK 3TOCFL 4