Saying ‘no’ is an important skill to develop when learning a new language. Because Mandarin Chinese does not have one simple way to say ‘no’, a bit of effort is needed to master the negative, particularly with verbs.
There are two ways to say ‘no’ in Chinese: 没有 (méiyŏu) and 不 (bù). The pronunciation of 没有 (méiyŏu) is does not change, but in everyday speech the 有 (yŏu) is often dropped. On the other hand, 不 (bù) does change to bú when followed by a forth-tone character. Otherwise the rules for when each is used are actually fairly simple.
First, 没有 (méiyŏu) can never be used with 是 (shì). This rule is completely reliable, so simply memorize it and live by it.
今天不是一月一号。(Jīntiān búshì yī yuè yī hào. Today is not January 1.)
我妹妹不是十岁。(Wǒ mèimei i búshì shí suì. My younger sister is not 10 years old.)
Next, 不 (bù) is used for the present and future time, as well as for habitual activities. Often the adverbs of time, including words like today, tomorrow, next week, usually, or regularly, indicate which of these is meant.
他现在不在。 (Tā xiànzài búzài. He’s not home now.)
我不喝酒。 (Wǒ bù hējiǔ. I don’t drink (as a habit, in general). )
while 没 (méi) is used when talking about the past. As with不 (bù), adverbs of time, including words like yesterday, last month, last year, before, or once long ago, are used to indicate when in the past something did not happen. Also, the past here includes the perfect tenses, those forms that used ‘have’ plus the past participle, as in ‘I have never been to Beijing’ or ‘He hasn’t eaten Dim sum recently’.
我没有去。(Wǒ méiyǒu qù. I didn’t go; I haven’t gone.)
昨天我没有上课。(Zuótiān wǒ méiyǒu shàngkè. I didn’t go to class yesterday.)
Since single 有 (yŏu) means “have”. So 没有 (méiyŏu) also means” not have”.
我没有钱。(Wǒ méiyǒu qián. I don’t have money.)
他没有时间。(Tā méiyǒu shíjiān. He doesn’t have time.)
In spoken Mandarin 没 is short form of 没有, so 有 (yŏu) is often omitted.
我没去过长城。（Wǒ méi qùguò chángchéng. I haven’t been to the Great Wall.）
我没汽车。（Wǒ méi qìchē. I don’t have a car.）