אחיין vs בן–אח Do the words mean the same? Which of them is the most common for "nephew"?

שמה vs שם What is the difference between שם and שמה? Both mean "there", but are they interchangeable ?

Butcher shop What is the common word for "butcher shop" in Hebrew? קצביה or אטליז ? What exactly is the difference between the two?

מטוס vs אוירון Is אוירון still used nowadays or is מטוס the most common word? If so, is there any difference between the two?

Pronunciation of חצי Apparently this word can be pronounced with either an /a/ or an /e/ sound as its main vowel. Is there a rule? Does it depend on the speaker?

I feel like laughing / בא לי לצחוק I've come across this ...בא ל expression in the sentence בא לי לצחוק. But is it a fixed expression or does it always have this meaning? Can I say something like בא לי ללכת לקולנוע (I feel like going to the movies)?

נשמה vs נפש What exactly is the difference between these two words? Both seems to mean "soul", "spirit".

חופשה vs נופש What exactly is the difference between חופשה and נופש? I believe both mean something like "holiday, vacation", but I don't really know when to use one or the other

Which spelling to use? How exactly are we supposed to decide which spelling to use? For instance, today I came across a word in the dictionary that had four possible spellings: לוין, לוויין, לווין, לויין. Ok, the first one is the defective spelling (used with niqqud)... but how does one choose between the others?