Verb + てもいい

This pattern is used to grant permission or to ask for permission to do something. It states that a particular action is allowed. Use the plain て-form + もいい for casual situations, and て-form + もいいですか to ask for permission politely. It is common in everyday situations like asking to borrow something, using facilities, or taking actions in someone’s presence. Remember this is about allowance (not obligation or prohibition); for prohibition you use 〜てはいけない instead.