Meaning of “since” - Learner’s Dictionary

since

conjunction uk us /sɪns/
TIME

B1 from a time in the past until a later time or until now:

He's been much happier since he started his new job.
I've known Tim since he was seven.
BECAUSE

B1 because:

He drove quite slowly since we had plenty of time.

(Definition of “since conjunction” from the Cambridge Learner’s Dictionary © Cambridge University Press)