This is the 749th most frequent Dutch word.
gewone
"Gewone" means "ordinary" or "common" in English.
Here, 'gewone' is used as an adjective describing the noun 'dag', meaning 'ordinary' or 'common'.
Dit is een gewone dag.
This is an ordinary day.
In this sentence, 'gewone' qualifies the noun 'mens', implying 'average' or 'normal'.
Een gewone mens kan dit probleem begrijpen.
An average person can understand this problem.
The word 'gewone' modifies 'thee', used here to mean 'plain' or 'regular' to distinguish from other types of tea.