Then / whereas (formal 则)

Structure Condition，(subject) 则 + result ／ A…，B 则… (contrast)

则 (zé) is a Classical Chinese connector now confined to written language, with two values. (1) CONDITION-RESULT, "then / in that case": 欲速则不达 = "if you want speed, then you won't arrive" (haste leads nowhere). (2) CONTRAST between two parallel members, "whereas / by contrast": 前者价格昂贵，后者则相对便宜 = "the former is expensive; the latter, by contrast, is relatively cheap". It is the cultured, compact version of 就 (conditional) and of 而 / 但是 (contrast); it always goes AFTER the subject of its clause, never at the very start.

Examples

欲yù速sù则zé不bù达dá。
Haste does not get you there.
前qián者zhě价jià格gé昂áng贵guì，后hòu者zhě则zé相xiāng对duì便pián宜yi。
The former is expensive; the latter, by contrast, is relatively cheap.
虚xū心xīn则zé进jìn步bù，自zì满mǎn则zé落luò后hòu。
Humility leads to progress, whereas complacency leads to falling behind.
理lǐ论lùn若ruò脱tuō离lí实shí际jì，则zé毫háo无wú意yì义yì。
If theory is divorced from practice, then it is utterly meaningless.

Levels are indicative: they follow the standard Chinese Grammar Wiki (AllSet Learning) progression, not an official HSK 3.0 mapping. We never assign levels by eye.

This point and the other 370, with audio on every example, inside Wanyu.