3 sentences

1. 假定他还没走，我们现在去还能见到他。

   jiǎ​dìng tā hái méi zǒu, wǒ​men xiàn​zài qù hái néng jiàn​dào tā.

   Assuming he hasn't left yet, we can still see him if we go now.

   Source: Dong Chinese Dictionary

2. 警察假定嫌疑人还留在城里，并封锁了所有的出口。

   jǐng​chá jiǎ​dìng xián​yí​rén hái liú zài chéng​lǐ, bìng fēng​suǒ le suǒ​yǒu de chū​kǒu.

   Assuming the suspect was still in town, the police blocked all the exits.

   Source: Dong Chinese Dictionary

3. 这只是一个假定的情况，并不是事实。

   zhè zhǐ​shì yī gè jiǎ​dìng de qíng​kuàng, bìng bù shì shì​shí.

   This is just a hypothetical situation, not a fact.

   Source: Dong Chinese Dictionary