When to use sin (not shin) ש or samekh ס in writing?

See a translation

@gen110888: that's a tricky subject you're getting into (and no, we're not all co-conspiring to pull the wool over your eyes by not disclosing the quintessentials of the furtive Hebrew grammar :) ). I have to admit I really don't know much about it. However, it was suggested in a handful of researches I got to randomly read, that there used to be some differences (at least among a section of the populace, if you're familiar with the 12 tribes of the ancient Israelites) between שֺ and ס. The Efraim tribe was said to be distinguishable from the rest by their characteristic lisping of שֺ (it's believed they pronounced it like 'th' in thick)

Not to douse your curiosity, but as an English speaker I would have imagined you'd be familiar with this phenomenon. When new English words were coined, did they just randomly choose to use 's' and 'c' (sell and cell, serenity and certainty), 'k', 'c', 'q' and 'ck' (can and kangaroo, pic, pick, peek and pique), 'f' and 'ph' (wharf and morph)...

Long story short, nothing man-made is usually arbitrary and reasonless, but as languages morph and change, they tend to retain these vestiges of their former origins, as long as massive spelling reforms don't take place.