〜たい: Expressing Your Own Desire

To say you want to do something in Japanese — eat, go, sleep, see — you attach 〜たい to a verb: 食べたい "I want to eat," 行きたい "I want to go." It looks like a tidy one-to-one swap for English "want to," and at the level of translation it is. But 〜たい behaves in two ways that surprise English speakers, and both flow from one fact: たい is not a modal verb, it is an adjective describing an inner state. That single reframing explains why it bends like 高い or 楽しい, and why you cannot use it to announce what somebody else secretly wants.

The form: ます-stem + たい

Take the ます-stem (連用形) — the same short stem that ます rides on — and add たい. Godan verbs shift to the い-row; ichidan verbs drop る; the two irregulars behave as expected.

The polite form is simply 〜たいです — you do not add ます to it (there is no ×行きたます). This is your first clue that たい has stopped being a verb and become something else.

たい inflects like an い-adjective

Here is the reframing English speakers most need. In English, "want to" never changes shape — I want to, I wanted to, I didn't want to all keep "want" intact and let other words do the tense and negation. In Japanese, 〜たい carries all of that itself, inflecting exactly like the い-adjective 高い. The final い is what moves.

Notice: no だ, no ます, no でした anywhere. たい → たくない → たかった → たくなかった is the い-adjective pattern (compare 高い → 高くない → 高かった → 高くなかった). Getting this wrong — reaching for ×行きたいだった or ×行きたいじゃない — is the tell of a learner treating たい as a verb or a noun.

Whose desire? たい is first person (second in questions)

Because たい describes a felt inner state — the pull of a craving, the ache of a wish — Japanese treats it as something you can only assert about yourself. You have direct access to your own wants and to nobody else's. So plain 〜たい is essentially a first-person form: I want to.

In a question, ownership shifts to the listener, so 〜たい naturally becomes second-person: you're asking about their want.

What you cannot do is flatly assert a third party's private want with plain たい. ×弟は日本へ行きたい ("my brother wants to go to Japan") claims direct knowledge of his inner state — it sounds like mind-reading. To report someone else's desire you either quote them, hedge with an evidential, or switch to the observational form 〜たがる:

The が / を alternation on the object

Here is a subtlety competing explanations often skip, and one English offers no parallel for. When the verb under たい is transitive, its object can be marked with either を or が:

Both are correct. The difference is one of focus. Marking the object with が pulls it into the spotlight of the desire — water is the thing I'm longing for, the craving is about it. This works because 〜たい is adjective-like, and the が-marked noun behaves like the thing the adjectival state is about (much as in 水がほしい). Marking it with を keeps the ordinary verb-and-object relationship intact and simply reports the wanted action.

A few practical tendencies:

• が is warmer, more emotional, and common with short, punchy cravings: ラーメンが食べたい, コーヒーが飲みたい.
• を is preferred when other words separate the object from たい, or when the sentence is longer and more matter-of-fact: 週末は新しい店でラーメンを食べたい.
• Modern casual speech drifts toward を, but が remains fully natural and is the more traditional, feeling-forward choice.

A note on register

〜たい plainly voices your own desire, which is friendly among peers but can feel too naked when aimed up at a superior. Telling your boss 社長に会いたいです ("I want to meet the president") is grammatically fine but a touch blunt; softening into the humble お会いしたいです, or the very deferential お目にかかりたいです (literary/formal), lands better. For wishes you're placing on someone else's action — "I want you to…" — たい is the wrong tool entirely; that job belongs to 〜てほしい.

Common mistakes

Key takeaways

• 〜たい = ます-stem + たい: 行き → 行きたい, 食べ → 食べたい. Never on the dictionary form (×食べるたい).
• It inflects as an い-adjective: たい → たくない → たかった → たくなかった. No だ, no ます.
• It is essentially first person (second in questions). You cannot flatly state another person's want with plain たい — quote, hedge, or use 〜たがる.
• The object may take が (craving in focus: 水が飲みたい) or を (neutral: 水を飲みたい) — a focus distinction English lacks.
• For wanting a thing rather than an action, use 〜がほしい; for wanting someone else to act, use 〜てほしい.