आप, तुम or तू: which Hindi word for “you” should you use?

Hindi has three words for “you”. आप (aap) is the formal one, used with strangers, elders and anyone senior. तुम (tum) is casual, used with friends, siblings and colleagues your own age. तू (tu) is intimate — reserved for very close friends and small children, and openly insulting to anyone else. When in doubt, use आप.

English gives you one word for the person you are speaking to. Hindi gives you three, and they are not interchangeable. Choosing wrongly does not produce a grammar error — it produces a social one, which is worse, because nobody will correct you.

This is also the single thing machine translation gets wrong most often, because a translation engine cannot know who you are talking to.

The three levels

आप is also the plural, which is why it doubles as the respectful form — addressing one person as though they were many is a politeness strategy Hindi shares with French vous and German Sie.

When in doubt, use आप

Over-formality is a small mistake. Under-formality is a real one. Calling your friend आप sounds slightly stiff and they will laugh. Calling a shopkeeper twice your age तू sounds openly disrespectful.

The safe default with anyone you have just met is आप, and you drop down to तुम only when they do it first, or when the relationship clearly warrants it.

तू is a trap for learners

Learners often meet तू in film songs and poetry, where it signals intimacy, and assume it is simply the casual option. In everyday speech it carries far more weight than that.

Between two lifelong friends, तू is warm. Directed at a stranger, it is a deliberate insult — it is what people use in an argument in traffic. Unless someone uses it with you first, leave it alone.

The verb has to follow

Getting the pronoun right is only half the job. Every verb in the sentence changes to match — and it also changes with the speaker's own gender. Mixing levels mid-sentence is the clearest sign of a translation produced by a machine.

Paste both of those into any general-purpose translation tool in English and watch how often the output mixes आप and तुम inside a single paragraph. It happens because each sentence is translated in isolation, with no memory of the one before it.

Regional and generational variation

• In much of Uttar Pradesh and Bihar, तू is used far more casually among family than it is in Delhi or Mumbai.
• Younger urban speakers often mix English into the same sentence, which sidesteps the choice entirely — 'aap busy ho?' is common.
• In writing, especially anything official, आप is effectively the only acceptable form.

The short version

• Meeting someone new: आप.
• They switch to तुम: you can switch too.
• You are not sure: आप. Nobody has ever been offended by too much respect.
• तू: only if you are certain, and never with a stranger.
• Whichever you pick, keep every verb in the sentence at that level.