Saying what you want with 欲しい and たい
Open chapter 1 and first use the word support directly below. Then read the 欲しいです example aloud and point to the desired thing.
1. A thing: noun + が欲しいです
欲しい expresses that the speaker wants to have something. The desired thing takes が: 新しい時計が欲しいです. 欲しい is an い-adjective here, not a verb, so do not attach を or ます to 欲しい.
Ask about the desired thing with 何が欲しいですか. The answer can replace the question word and keep the same structure.
何が欲しいですか。
新しい時計が欲しいです。
2. An action: ます-stem + たいです
For something you want to do, take the polite verb form, remove ます, and add たいです. 飲みます becomes 飲みたいです; 行きます becomes 行きたいです.
With a します verb, the stem ends in し: 旅行します → 旅行したいです. Keep other sentence parts: 北海道へ行きます becomes 北海道へ行きたいです.
3. Desired thing or desired action
First decide what follows ‘want’. A thing such as a camera fits カメラが欲しいです. An action such as going to Japan fits 日本へ行きたいです.
With the direct object of a たい verb, both を and が are possible: 水を飲みたいです and 水が飲みたいです are both natural. The bounded writing exercise below accepts both forms. Other particles keep their own roles: a destination in 図書館へ行きたいです takes へ. Ask 何が欲しいですか about a thing, 何をしたいですか about an activity, and どこへ行きたいですか about a destination.
カメラが欲しいです。
日本語を勉強したいです。
4. Build your own wish
First choose one concrete thing and one action you can perform. For the thing, build Xが欲しいです. For the action, find the familiar ます-form, remove only ます, and add たいです.
In this free task, speak about your own or a fictional wish. Avoid firm claims about what another person wants if they have not said so themselves.