HSK 7–9 grammar · conjunction
倘若/假设/假使/若⋯⋯，就/那（么）⋯⋯
倘若/假设/假使/若⋯⋯，就/那么⋯⋯ — if …, then …
Pattern
+ +
( ) can be left out · other words may come before, between and after
How it works
The full conditional frame: a formal "if" word opens the supposition and 就 or 那么 introduces the consequence. 假设 and 假使 lean towards hypotheses set up for argument, 倘若 and 若 towards contingencies that may really occur.
Examples
假使明天下雨，那么活动就取消。
Jiǎshǐ míngtiān xià yǔ, nàme huódòng jiù qǔxiāo.
If it rains tomorrow, the event will be cancelled.
假设这个数据是对的，就说明方法有效。
Jiǎshè zhège shùjù shì duì de, jiù shuōmíng fāngfǎ yǒuxiào.
Assuming this figure is right, it shows the method works.
Related
See it in a story
In the app, 倘若/假设/假使/若⋯⋯，就/那（么）⋯⋯ is underlined wherever it appears in the stories you read, and practised with sentences from them. Free.