What is the たい Form?
The たい form is how you say you want to do something: "I want to eat," "I want to go," "I want to sleep." It attaches to a verb, which is what separates it from ほしい — ほしい is for wanting a thing, たい is for wanting to do an action.
It is one of the first patterns worth mastering, because it turns a vocabulary list into something you can actually say. Our lesson on likes and wants covers it alongside 好き and ほしい.
How to Form It
Take the ます stem — the ます form with ます removed — and add たい.
| Dictionary | ます form | たい form |
|---|---|---|
| 食べる | 食べます | 食べたい |
| 行く | 行きます | 行きたい |
| 飲む | 飲みます | 飲みたい |
| する | します | したい |
| 来る | 来ます | 来たい |
There are no group-by-group rules to memorise here. If you can make the ます form, you can make the たい form.
It Conjugates Like an い-Adjective
This is the part learners miss. たい is not a verb ending — the result behaves as an い-adjective, and conjugates like one.
| Affirmative | Negative | |
|---|---|---|
| Non-past | 行きたい | 行きたくない |
| Past | 行きたかった | 行きたくなかった |
So "I didn't want to go" is 行きたくなかった, never ×行きたいじゃなかった.
を or が?
Both appear, and both are correct:
- 水を飲みたい。
- 水が飲みたい。
を keeps the normal object marking and is the safer default. が puts more feeling on the thing itself — closer to "it's water that I want." が is more common with short, strong statements.
Only for Yourself
This is the rule that trips people up. たい describes your own desire. Saying 田中さんは行きたいです sounds like you are reading someone else's mind.
To talk about what someone else wants, use one of these instead:
- たがっている — 田中さんは行きたがっている。(Tanaka wants to go.)
- quote them — 田中さんは行きたいと言っていました。(Tanaka said they want to go.)
Questions are fine, though — 何が食べたいですか is a normal thing to ask, because you are asking about the listener's own desire.
Making It Polite
Add です, exactly as with any い-adjective:
- 行きたいです。(I want to go.)
- 行きたくないです。(I don't want to go.)
For an invitation, たい is usually the wrong tool — 行きたいですか can sound blunt. Use ませんか instead: 一緒に行きませんか。