question about variations of a phrase
 

how many variations are there of 'i'm so sleepy?

difference between nemui, nemuru, nemurutai & nemu?

I say 眠い(ねむい/nemui)　or すごく/とても眠い（sugoku/totemo nemui), but I don't say nemurutai.

nemuru=to sleep.
namuri-tai (not nemuru-tai)=(I) want to sleep.

I often say 'ねむたいnemutai' 'ねむっ！nemu!' etc. but I think they're colloquial.　(It's more colloquial with 'た/ta'.)

I always favored 超疲れたぜ！

then how would you say 'i need sleep' ?

寝なければならない。
寝ないとだめだ。
睡眠が必要だ。

or 寝なくちゃいけません。　 i have to sleap.
寝たい。　 i want to sleep.

but kyle's phrases are probably more natural-sounding.

Grammatical but extremely bookish. You would almost never hear anyone say it.

This is read 「ねたい」 and, at least around Tokyo, it usually means somethng I cannot say here. "Wanna xxxx you/her."

It is 「眠（ねむ）たい」.
________

As Sumippi stated, 「眠（ねむ）い」 is also very natural-sounding.

All are 100% grammatical but I cannot think of a situation where anyone would say any of these.

First one sounds plain textbook to me. The last two, the very last one in particular, sound as if you were saying that one must sleep to live.

True. I was just throwing them out because OP asked for all the variations. :)

笑(^O^)


'I need sleep'... I'd say「寝なきゃ(nenakya)」「寝ないと(nenai-to)」「寝なくちゃ(nenakucha)」or maybe「寝なくっちゃ(nenakuccha; might sound a bit childish...maybe)」. These are all contracted forms of 寝なくてはいけない(nenakutewa-ikenai).　But I always say 寝なアカン(nena-akan) or 寝な(nena, in a falling tone) because...I speak Kansai dialect.

寝たい(Netai) as 'I want to sleep' might be OK only when you use it as part of longer sentences, like・・・「もうそろそろ寝たいんですけど。」「寝た� �と思っているのに、目がさえて・・・。」「早く寝た� �けど、まだ宿題がある。」etc.