Giving reasons (conjunction): since=because
- I like this park because it is close to my house.
- I like this park since it is close to my house.
Passage of time
- I have been working here since 2005. (preposition)
- Since I was a child I have loved the Beatles. (conjunction)
From then until now; at a subsequent time (adverb)
- Jenny left class at 9 am and hasn't been back since.
- Mary graduated last year. She has since gotten a job and moved to California.