可以 (kěyǐ) is primarily used for expressing permission in Chinese grammar.

Structure
Permission is expressed with the auxiliary verb 可以. It might be helpful to think of 可以 as meaning "may." This will help to keep its functions and usage clear.

Use this structure to express permission to do things.

Examples

Nǐ ké yǐ zuò zài zhè'ér.
你 可以 坐 在 这儿。
You may sit here.