'可以' (kě yǐ) is a modal verb expressing ability, permission, or possibility — equivalent to 'can', 'may', or 'be able to'. The character 可 means 'acceptable' or 'feasible', and 以 originally meant 'to use' or 'by means of'; together, they convey the idea of something being feasible or permissible under given conditions. Unlike English 'can', which often implies physical ability, '可以' frequently signals social permission or practical possibility — for example, asking if an action is allowed or whether something is viable.

This word appears in questions ('我可以...？'), statements ('你可以...'), and negatives ('不可以'). It's neutral in register — used in both casual speech and formal writing — and commonly follows subjects directly without additional auxiliaries. It does not conjugate for tense or person, and its meaning relies heavily on context: '我可以喝水' could mean 'I’m allowed to drink water' or 'I’m able to drink water', depending on situation.