Do For Someone (~te ageru)

~てあげる is used when the speaker (or someone in the speaker's in-group) does something as a favor for another person. It emphasizes the kindness or helpfulness of the action. The recipient of the favor is marked with に.

Important social note: using てあげる directly to the person you're helping can sound condescending or boastful, as if you're highlighting your own generosity. It is safer to use it when talking about favors to a third party. When offering help directly, use ましょうか (shall I?) or the simple te-form + ください pattern instead.

The polite/humble equivalent is ~てさしあげる, used when the recipient is someone of higher status. In casual speech, ~てやる is sometimes used instead of ~てあげる, though it can sound rough or condescending depending on context. ~てやる is appropriate when talking about doing something for animals, plants, or children.