This is the 447th most frequent Lithuanian word.
kasdien
"Kasdien" means "every day" in English.
Here, 'kasdien' is used as an adverb modifying the verb 'einu' (I go), indicating the frequency of the action, meaning 'every day'.
Aš kasdien einu į darbą.
I go to work every day.
In this sentence, 'kasdien' is again functioning as an adverb indicating the frequency of occurrence of the action 'matomės' (we meet), specifying that it happens every day.
Mes matomės kasdien vakare.
We meet every evening.
Here, 'kasdienis' is an adjective derived from 'kasdien', describing 'gyvenimas' (life), indicating something that pertains to every day, meaning 'daily'.