kyou wa hayaku netai desu.

topic particle

Breakdown of kyou wa hayaku netai desu.

• です: to be
• 今きょ日う: today
• 〜たい: to want to

Questions & Answers about kyou wa hayaku netai desu.

What does は do in 今日 は 早く 寝たい です? Why not が or nothing?

は marks 今日 (today) as the topic of the sentence: “As for today, I want to go to bed early.”

• が would mark something as the grammatical subject or as something being contrasted/focused, and 今日が早く寝たいです is not natural.
• Leaving out は (今日早く寝たいです) is possible in casual speech, but feels a bit abrupt. Using は makes the sentence feel neatly framed: “Today, (at least), I want to sleep early.”

Why is it 早く and not 早い?

早い (hayai) is an i-adjective meaning early/fast.
早く (hayaku) is its adverb form, meaning early/quickly.

In Japanese, verbs are usually modified by adverbs, not adjectives:

• 早い 寝たい → incorrect / unnatural (adjective before verb)
• 早く 寝たい → correct (adverb before verb)

So 早く 寝たい literally means “want to sleep early” or “want to go to bed early”.

What exactly is 寝たい? Is it a verb form or an adjective?