Formal:
* 明白 (míngbai) - This is the most common and general way to say "understand."
* 理解 (lǐjiě) - This implies a deeper understanding or comprehension.
* 清楚 (qīngchǔ) - This means "clear" and indicates understanding something completely.
Informal:
* 懂 (dǒng) - This is a casual way to say "understand."
* 知道 (zhīdào) - This literally means "know" but can also be used to mean "understand."
Examples:
* 你明白我的意思吗？ (Nǐ míngbai wǒ de yìsi ma?) - Do you understand what I mean?
* 我理解你的感受。 (Wǒ lǐjiě nǐ de gǎnshòu.) - I understand your feelings.
* 我清楚你的想法。 (Wǒ qīngchǔ nǐ de xiǎngfǎ.) - I understand your thoughts.
* 你懂我的意思吧？ (Nǐ dǒng wǒ de yìsi ba?) - You understand what I mean, right?
* 我知道你在说什么。 (Wǒ zhīdào nǐ zài shuō shénme.) - I know what you are saying.
You can also use a combination of these words to create more nuanced meanings. For example, you could say:
* 我明白你意思，但我理解你的感受。 (Wǒ míngbai nǐ yìsi, dàn wǒ lǐjiě nǐ de gǎnshòu.) - I understand what you mean, but I understand your feelings.
Ultimately, the best way to say "understand what" in Chinese will depend on the specific situation and the level of formality you want to convey.