This is the 105th most frequent Slovenian word.
ker
"Ker" means "because" in English.
The word 'ker' is used here as a conjunction to introduce a clause giving the reason for the prior action or state.
Včeraj nisem prišel, ker sem bil bolan.
I didn't come yesterday because I was sick.
The word 'ker' links two clauses, explaining the motivation for the action of buying in the first clause.
V trgovini sem kupil kruh, ker je bil v akciji.
I bought bread at the store because it was on sale.
Here, 'ker' indicates causality, showing the reason behind the preference to stay home.