She listens to music when she takes a walk.
Chinese: Her walking times (she) listens to music.
Tā sànbù de shíhou tīng yīnyuè.
她散步的时候听音乐。
English: They watch TV when (while) they eat dinner.
Chinese: When (while) they eat dinner, they watch TV.
Tāmen chī wǎnfàn de shíhou kàn diànshì .
他们吃晚饭的时候看电视。
However, if by “when” you mean “after . . . ,” then “when . . . ” is translated as yǐhòu 以后:
When (after) I graduate, I’m going to China to teach English.
✔ CC: Wǒ bìle yè yǐhòu dào Zhōngguó qù jiāo Yīngyǔ.
我毕了业以后到中国去教英语。
✖ BC: Wǒ bìyè de shíhou dào Zhōngguó qù jiāo Yīngyǔ.
我毕业的时候到中国去教英语。
When I’m graduating, just as I’m walking up to get my diploma, I’m already on my way to China! (Is the graduation hall on the way, or am I grabbing my diploma as I get on the plane?!)
✖ BC: Yǐhòu wǒ bìyèle dào Zhōngguó qù jiāo Yīngyǔ.
以后我毕业了到中国去教英语。
That’s because 以后 and 以前 never come BEFORE what they refer to!
(2) To say “again”: zài 再 vs. yòu 又
When you say that someone will do something again in the future, use zài 再:
I will go to China again next year.
Wǒ míngnián huì zài dào Zhōngguó qù.
我明年会再到中国去。
We’re going to see that movie again tomorrow evening.
Wǒmen míngtiān wǎnshang huì zài kàn nèige diànyǐng.
我们明天晚上会再看那个电影。
When you say something happened again in the past, use yòu 又:
I went to China again last year.
Wǒ qùnián yòu dào Zhōngguó qù le.
我去年又到中国去了。
We saw that movie again last night.
Wǒmen zuótiān wǎnshang yòu kàn le nèige diànyǐng.
我们昨天晚上又看了那个电影。
However, be aware that before certain helping verbs, such as shì 是 (am, is, are), xiǎng 想 (think), néng 能 (can/able to), yào 要 (want), yǐhòu 以后 (after), and huì 会 (can/know), you can only use yòu 又 (again, regardless of tense):
Tomorrow there’s going to be a test again.
Míngtiān yòu shì yíge kǎoshì.
明天又是一个考试。
They need to/want to see the doctor yet again this afternoon.
Tāmen jīntiān xiàwǔ yòu yào qù kàn dàifu.
他们今天下午又要去看大夫。
(3) “After”/“later”: yǐhòu 以后 vs. ránhòu 然后
When you say that someone will do something and then afterward/later will do something else in the future, or that someone generally does something and then afterward/later does something else, you can either use yǐhòu 以后 or ránhòu 然后 for “after that”/“afterward”/“later.”
However, depending on which of the two expressions you use, the structure of the sentence will be different:
After she goes to class, she’ll go work.
Tā xià le kè yǐhòu jiù huì qù gōngzuò.
她下了课以后就会去工作。
OR:
She’s in class right now, and afterward will go work.
Tā xiànzài zhèngzài shàngkè, ránhòu tā huì qù gōngzuò.
她现在正在上课, 然后她会去工作。
You cannot use hòulái 后来, which is only used for actions in the past.
✖ BC: Tā xiànzài zhèngzài shàngkè, hòulái tā huì qù gōngzuò.
她现在正在上课, 后来她会去工作。
Every evening they watch TV, and after that they go to bed.
✔ CC: Tāmen měitiān wǎnshang kànle diànshì yǐhòu jiù shàngchuáng.
他们每天晚上看了电视以后就上床。
了 is used here because you’re really saying: “Having watched TV, they then go to bed.”
OR:
✔ CC: Tāmen měitiān wǎnshang kàn diànshì, ránhòu jiù shàngchuáng.
他们每天晚上看电视, 然后就上床。
了 is NOT used here because you’re saying: “They watch TV, and after that they go to bed.
✖ BC: Tāmen měitiān wǎnshang kàn diànshì, hòulái jiù shàngchuáng.
他们每天晚上看电视, 后来就上床。
However, there is a difference between the use of yǐhòu 以后 and ránhòu 然后. Ránhòu 然后 always implies that one action logically or naturally follows the other, whereas yǐhòu 以后 can be used even with two actions that are not necessarily a logical or natural sequence. As a result, ránhòu 然后 cannot be used with a negative clause:
He’s working at a factory this year, but afterward he doesn’t plan to work there any more.
✔ CC: Tā jīnnián zài gōngchǎnglǐ gōngzuò, kěshì yǐhòu tā bùdǎsuan zài nèr gōngzuò le.
他今年在工厂里工作，可是以后他不打算在那儿工作了。
✖ BC: Tā jīnnián zài gōngchǎnglǐ gōngzuò, kěshì ránhòu tā bùdǎsuan zài nèr gōngzuò le.
他今年在工厂里工作，可是然后他不打算在那儿工作了。
The use of hòulái 后来 vs. ránhòu 然后
When you say that someone did something in the past and after that or later did something else, or that someone regularly did something in the past and after that or later did something else, use either hòulái 后来 or ránhòu 然后. Unlike yǐhòu 以后, neither can be used after the verb in the first clause, but must be placed at the beginning of the second clause.
Mr. Wang taught Chinese in college for twenty years, and after that retired.
✔ CC: Wáng Xiānsheng zài dàxué jiāole èrshíniánde Hànyǔ, hòulái jiù tuìxiū le.
王先生在大学教了二十年的汉语，后来就退休了。