Learn Italian: Ho molto sonno perché è notte. - I'm very sleepy because it's nighttime.

In Italian, physical states like being sleepy, hungry, or thirsty are expressed using the verb avere (to have) followed by a noun. Instead of saying "I am sleepy", Italians say ho sonno, which literally means "I have sleepiness".

If sonno means "sleep", why does molto sonno translate to "very sleepy"?

Because sonno is a noun, you cannot use a word for "very". Instead, you say you have "much sleep" or "a lot of sleep". Molto is acting as an adjective here to describe the amount of sleepiness you have.

Does perché mean "because" or "why"?

It means both! In Italian, perché is used both to ask a question ("why?") and to give a reason ("because"). Here it connects the two ideas to mean "because".

Where is the word for "it" in è notte?

Italian doesn't use a dummy subject pronoun like "it" for facts, time, or weather. You just use the verb directly. So, è notte literally translates to just "is night".