preposition / conjunction / adverb
since
SINS/sɪns/
From a specified past time onward.
The runner has continued moving since starting the stopwatch.

Etymology
Middle English sithenes grew from an expression meaning “after that.” A stated event supplies the “that”: it marks the starting point for the period that follows.
In context
Batman has been around since 1939 and in that time there have been an insane number of interpretations of the character and mythology
More examples
- We have not spoken since Monday.
- It has rained ever since.
- Since arriving, he has made friends.
Forms
since
Similar words
- from
- Can mark a starting point, but may require onward or a changed tense to express continuing duration.