This is the 6177th most frequent Chinese word.
平常
Ordinary; usual; commonly.
In this sentence, '平常' is used as an adverb meaning 'usually' to describe a habitual action.
平常我们会去公园散步。
Usually, we go to the park for a walk.
Here, '平常' is used as an adjective meaning 'ordinary' to characterize his attire.
他的穿着很平常，没有什么特别。
His attire is very ordinary, nothing special.
'平常' in this case functions as an adjective modifying '日子' (days), indicating non-special occasions.