Usages of

  shì 老师lǎoshīwǒ bú shì lǎoshī.
I am not a teacher.

Note how (falling tone) changes it's pronunciation to (rising tone) when followed by a falling tone.

zhè  rén  shì 老师lǎoshīzhè gè rén bú shì lǎoshī.
This person is not a teacher.
  yào cháwǒ bú yào chá.
I don’t want tea.
  chī 米饭mǐfànwǒ bù chī mǐfàn.
I don’t eat rice.
  yào shuǐ yào  bēi cháwǒ bú yào shuǐ,wǒ yào yì bēi chá.
I don’t want water; I want a cup of tea.
昨天zuótiān  gēn  shuō   néng zuótiān wǒ gēn tā shuō wǒ bù néng qù.
Yesterday I told her I couldn’t go.
因为yīnwèi  hěn máng, 所以suǒyǐ   néng gēn  一起yìqǐ  kàn 电影diànyǐngyīnwèi wǒ hěn máng, suǒyǐ wǒ bù néng gēn nǐ yìqǐ qù kàn diànyǐng.
Because I am very busy, I can’t go watch a movie with you.
如果rúguǒ   lái, 我们wǒmen jiù 明天míngtiān zài rúguǒ tā bù lái, wǒmen jiù míngtiān zài qù.
If she doesn’t come, we’ll go again tomorrow.
如果rúguǒ   dēng guān le,  jiù  kàn shūrúguǒ nǐ bǎ dēng guān le, wǒ jiù bù kàn shū.
If you turn off the light, I won’t read.
今天jīntiān  yǒu 事情shìqíng,   kàn 电影diànyǐngjīntiān wǒ yǒu shìqíng, bù qù kàn diànyǐng.
I have things to do today; I’m not going to watch a movie.
虽然suīrán   认识rènshi  de 同事tóngshì, 但是dànshì  xiǎng 认识rènshi suīrán tā bú rènshi wǒ de tóngshì, dànshì tā xiǎng rènshi tā.
Although she doesn’t know my coworker, she wants to get to know him.
   认识rènshi  jiǔ, 但是dànshì 我们wǒmen 常常chángcháng 一起yìqǐ  超市chāoshìwǒ hé tā rènshi bù jiǔ, dànshì wǒmen chángcháng yìqǐ qù chāoshì.
He and I haven’t known each other for long, but we often go to the supermarket together.
 以前yǐqián  dǒng zhè  意思yìsiwǒ yǐqián bù dǒng zhè gè yìsi.
I didn’t understand this meaning before.
  huì yòng,  可以kěyǐ gěi  kàn 一下yíxià mawǒ bù huì yòng, nǐ kěyǐ gěi wǒ kàn yíxià ma?
I don’t know how to use it; could you show me for a moment?
qǐng  认真rènzhēn de kàn, 然后ránhòu 告诉gàosu   dǒng  dǒngqǐng nǐ rènzhēn de kàn, ránhòu gàosu wǒ nǐ dǒng bù dǒng.
Please look carefully, then tell me whether you understand.
我们wǒmen 晚上wǎnshang 睡觉shuìjiào 以前yǐqián  kàn 电影diànyǐngwǒmen wǎnshang shuìjiào yǐqián bù kàn diànyǐng.
We don’t watch movies before going to sleep at night.
 一般yìbān 周末zhōumò  上班shàngbān, huì gēn 家人jiārén chī 午饭wǔfàntā yìbān zhōumò bú shàngbān, huì gēn jiārén chī wǔfàn.
She usually doesn't work on weekends and will have lunch with her family.
医生yīshēng shuō  de 身体shēntǐ  tài hǎo, yào zài 医院yīyuàn 休息xiūxiyīshēng shuō tā de shēntǐ bú tài hǎo, yào zài yīyuàn xiūxi.
The doctor said his health isn’t very good and that he needs to rest in the hospital.
明天míngtiān 我们wǒmen 提前tíqián shí 分钟fēnzhōng 出发chūfā, jiù  huì 迟到chídào lemíngtiān wǒmen tíqián shí fēnzhōng chūfā, jiù bú huì chídào le.
Tomorrow we'll set off ten minutes early, then we won't be late.
我们wǒmen shì zuò 地铁dìtiě  医院yīyuàn de, piào   guìwǒmen shì zuò dìtiě qù yīyuàn de, piào yě bú guì.
We went to the hospital by subway; the tickets weren’t expensive.
周末zhōumò     自行车zìxíngchē,  kāi chēzhōumò wǒ hé tā qí zìxíngchē, bù kāi chē.
On weekends she and I ride bicycles and don't drive.
我们wǒmen shì  自行车zìxíngchē  de,  shì zuò 地铁dìtiě  dewǒmen shì qí zìxíngchē qù de, bú shì zuò dìtiě qù de.
We went by bicycle, not by subway.
地铁dìtiě de piào  guì, 公交车gōngjiāochē de piào gèng 便宜piányidìtiě de piào bú guì, gōngjiāochē de piào gèng piányi.
Subway tickets are not expensive; bus tickets are even cheaper.
今年jīnnián 周末zhōumò  xiǎng gēn 家人jiārén zài jiā,  打算dǎsuàn 出去chūqù lejīnnián zhōumò wǒ xiǎng gēn jiārén zài jiā, bù dǎsuàn chūqù le.
This year on weekends I want to be at home with my family; I don't plan to go out.
今天jīntiān   kāi chē,  zuò 地铁dìtiějīntiān wǒ bù kāi chē, wǒ zuò dìtiě.
I'm not driving today; I'm taking the subway.
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