夜更かしはいけない。

夜更かしはいけない。

You must not stay up late.

夜(よる)更(ふ)かしはいけない。

Yoru fukashi waikenai.

夜 (よる、よ)

evening; night

更かす (ふかす)

to sit up late

ば (ば)

if ... then; when; and; why don't you...?; the more (one does something); because; since

Readings: ヤ、よ、よる

Meanings: night, evening

Readings: コウ、さら、さら.に、ふ.ける、ふ.かす

Meanings: grow late, night watch, sit up late, of course, renew, renovate, again, more and more, further