Formal:
* 文盲 (wén máng): This is the most common and formal term for "illiterate" in Chinese. It literally means "blind to literature," and it implies a lack of basic literacy skills.
Informal:
* 不识字 (bù shí zì): This means "not knowing characters," and it implies a lack of ability to read and write. It is a more informal way of saying "illiterate."
* 目不识丁 (mù bù shí dīng): This is a more colloquial phrase that literally means "eyes not knowing 'ding'," which is the first character in the Chinese alphabet. It's a more playful and casual way to say "illiterate."
Note: It's important to be mindful of the context when using these terms, as they can be sensitive depending on the situation.