since
conj.used to give a reason for something. You use it when the person you are talking to already knows the facts you are mentioning.
conj.used to introduce a subordinate clause that provides a reason or explanation for the main clause. Often implies that the reason is already known to the listener or is a logical consequence of the situation.
“Since it is raining, we should stay inside.”
“Since the office is closed for the holiday, all staff members are working from home today.”
“Since the initial data proved inconclusive, the research team decided to extend the study for another six months to ensure the results were statistically significant.”
When used as a conjunction of reason, it typically appears at the beginning of a sentence or after a comma.
since vs for — Since marks the specific starting point of an action, while for measures the total duration of the period.
since vs from — Since marks the start of a period that continues until now, while from marks a starting point without implying the action is still happening.
Learners often use 'since' to describe a duration of time; 'since' must refer to a specific starting point, while 'for' describes the length of time.
Usage since the start · since early · since records
From Middle English syns, synnes, contraction of earlier sithens, sithence, from sithen (“after, since”) ( + -s, adverbial genitive suffix), from Old English sīþþan, from the phrase sīþ þǣm (“after/since that (time)”), from sīþ (“since, after”) + þǣm dative singular of þæt. Cognate with Dutch sinds (“since”), German seit (“since”), Danish siden (“since”), Icelandic síðan (“since”) Scots syne (“since”).
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.