If / supposing… (倘若/倘使)

Structure 倘若/倘使 + supposition，（则/便）+ consequence

倘若 (tǎngruò) and its variant 倘使 (tǎngshǐ) introduce a condition in a formal, written register: "if…", "in the event that…". They mean the same as 如果 / 要是 (HSK 1–3) but sound far more literary, appearing mostly in journalism, essays and polished prose. The consequence is often capped with 则 (zé) or 便 (biàn) — also formal — rather than colloquial 就. It is common in warnings and reasoning: 倘若属实，后果不堪设想 = "if it proves true, the consequences would be unthinkable".

Examples

倘tǎng若ruò消xiāo息xī属shǔ实shí，后hòu果guǒ不bù堪kān设shè想xiǎng。
If the news proves true, the consequences would be unthinkable.
倘tǎng使shǐ各gè方fāng拒jù不bù让ràng步bù，谈tán判pàn则zé将jiāng彻chè底dǐ破pò裂liè。
Should the parties refuse to make concessions, the talks will break down completely.
倘tǎng若ruò人rén人rén都dōu袖xiù手shǒu旁páng观guān，社shè会huì便biàn无wú从cóng进jìn步bù。
If everyone simply stood by, society would have no way to advance.
倘tǎng若ruò当dāng年nián另lìng作zuò选xuǎn择zé，他tā的de人rén生shēng或huò许xǔ截jié然rán不bù同tóng。
Had he chosen differently back then, his life might have been entirely different.

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.