This is the 58th most frequent Chinese word.
小
Small.
The word '小' is used here as an adjective describing the size of the cup.
他喜欢喝小杯咖啡。
He likes to drink small cups of coffee.
The word '小' is used here in a compound word '小时候' meaning 'when I was little', referring to a younger age.
我小时候住在乡下。
When I was little, I lived in the countryside.
The word '小' is used here to express the significance of the problem in the phrase '不小', meaning 'not small' or 'significant'.