點 - in terms of time, this means o'clock 現在幾點了？ What's the time now? 3點 - 3 o'clock // 現在幾點？ What's the time? 4點半 - 4:30 鐘頭（兒） and 小時 both mean hour 從這個地方開車到那個地方要兩個鐘頭 - it takes two hours to drive from here to there by car I have never seen anybody use 天色 時間 also translates as time, but is used for periods of time. 離夏天還有連個禮拜的時間 - there are still two weeks before summer 鐘 is added when you talk about minutes and seconds 三十分鐘 - 30 minutes / 九十秒鐘 - 90 seconds Laurence

I would add, 3 o'clock 三点 is same with 三点钟。 三个钟头： 3 hours. it is same with 三个小时。 how many hours do you use to learn Chinese after 6 o'clock you get up? This is the time of morning. That time of the day(color of sky) is early(morning)你早上用6点之后的几个小时去学中文？那个是早上的时间。那时天色很早。 sān diǎn (right) 三点 sān zhōng diǎn (wrong) san ge zhong 三个钟/Zhōng diǎn gōng 钟点工 sān zhōng tóu (wrong) Sān gè zhōng tóu 三个钟头 sān ge xiǎo shí 三个小时 (right) sān tiān sè no this statement. 天色早，Tiān sè zǎo天色晚 Tiān sè wǎn sān shí jiān. 三时间，no this statement. shí jiān时间=time. measure word：Diǎn 点=hour

天色 tiān sè It's kind of use the color of the day to tell the approximate time, sometimes we say 天色还早（which means it's still early) or 天色已晚（literally means The sky had gone dark) if you want to say "3 o'clock". 3点 sān diǎn is correct.

You can say"三点（sān diǎn）“ or ”三点钟（sān diǎn zhōng）“. Both of them are correct. In fact, ”钟点“（zhōng diǎn） is not used frequently in Chinese when we talk about the time. Until I have written this answer, I can only remember one example of the use of it in Chinese. Well, there are hotels near the airports or train stations that called "钟点房", where people can have a short term rest. ( Here, "房" means "房间", a room.) "钟头”and“小时” tend to mean "a period of time". When someone asks "How long", we can use them to show the length of time. And, "钟头" is more likely to be a kind of common saying in Chinese widely used in rural. In my memory, my grandparents often used it to talk about the time. :D "天色" mean a general estimate of the time in one day. In the past, clock is rare so that people learnt to tell the time of day by the position of the sun or other ways. "天" means the sky and "天色" means the condition of the sky or the general time in one day. "时间" can be directly translated into "time". But mostly we do not use it after the number to show "what the time it is". Hoping to help.