Nighttime is the hours of night — the dark part of the day, when most people sleep.

Nighttimenighttime（夜間） is the hours of night指的是夜晚的時段 — the dark part of the day, when most people sleep一天裡黑暗的那部分，大多數人在睡覺的時候。

You can say at nighttime or in the nighttime, but learners should know that at night is the more common, lighter phrase for the same idea. Nighttime can also sit in front of another noun: nighttime hours, the nighttime sky.

You can say at nighttime or in the nighttime你可以說at nighttime或in the nighttime, but learners should know that at night is the more common, lighter phrase for the same idea但學習者應該知道，at night才是同樣意思裡比較常見、比較輕鬆的說法。Nighttime can also sit in front of another nounnighttime也可以放在另一個名詞前面: nighttime hours, the nighttime skynighttime hours（夜間時段）、the nighttime sky（夜空）。

It feels a little more formal or more “written” than plain night.

It feels a little more formal or more "written" than plain night它聽起來比單純的night更正式一點，或者說更「書面」一點。

Do not confuse it with overnight (covering the night as a stay or a journey) or with nightly (every night). Nighttime is the stretch of time; nightly is how often something happens.

Do not confuse it with overnight不要把它跟overnight搞混 (covering the night as a stay or a journey)（指整晚的住宿或旅程） or with nightly或nightly (every night)（每晚）。Nighttime is the stretch of timenighttime指的是那段時間本身; nightly is how often something happensnightly指的是一件事發生的頻率。

You may also see it as two words, night time, or with a hyphen, night-time, especially in British English.

You may also see it as two words, night time你也可能看到把它拆成兩個字寫成night time, or with a hyphen, night-time或加上連字號寫成night-time, especially in British English尤其是在英式英文裡。