When can I use "since" and "for" in their meaning of "because", and what is the difference? Is there any context related difference, because to me it seems that they are synonyms, but I recently found out that they weren't.

Hi, you use "since" if you are referring to a particular time, for example since 2012, since yesterday, since Wednesday and so on. On the other hand, you use "for" if you are talking about a range of time e.g for two years, for a decade, for four days. Summarily, "since" for a particular time, "for" is for a range or period of time. I hope this helps. I am new on this site, you may look for me for further correspondence or lessons. Good luck!