Since: Adverb, Preposition, and Conjunction

Since is often used to indicate time, but it can also be used for giving reasons, and in this sense is interchangeable with because. Be careful, however: because is not always interchangeable with since.

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.