The aux verbs たい and たがる both express “to want“, but they are not as straightforward to use as “want”.
たい expresses wishes and desires.
- 冷たい物が飲みたい -> I want to drink something cold
- 大きくなったら野球選手になりたい -> I want to be a baseball player when I grow up
- 外国に住みたいな -> I want to live abroad
- 馬鹿な事を言うのは止めて頂きたい -> I’d like you to stop talking nonsense
- 何か飲みたい？ -> You wanna drink something?
- 何かお飲みになりたいですか？ -> Would you like to drink something?
In writings and/or formal speeches, たい is often accompanied by と思う.
- 宇宙の起源について研究したいと思います -> I want to research the origin of the universe
- 宇宙の起源について研究したいです -> Not wrong, but sounds conversational
たい cannot be used for a third party, unless followed by と思っている, そうだ, らしい, etc..
彼女は女優になりたい- 彼女は女優になりたいと思っている -> She (is thinking she) wants to be an actress
- 彼女は女優になりたいそうだ -> I heard she wants to be an actress
- 彼女は女優になりたいらしい -> It seems like she wants to be an actress
たがる is used for a third party only.
- うちの子供が遊園地に行きたがっている -> My kids want to go to an amusement park
- 私はビールが飲みたい
(飲みたがる)-> I want to drink beer - 少し休憩したいですか？
(休憩したがりますか？)-> Would you like to take a little break?
However たがる comes with a big caveat: It often implies someone is wanting to do something unreasonably, annoyingly, frivolously and/or insincerely.
- うちの子供はやたらとゲームをしたがる -> My kid wants to play games excessively
- 彼女は何でも高価な物を欲しがる -> She wants expensive stuff, whatever it is
- 彼女は人の事に首を突っ込みたがる -> She wants, loves, to meddle with other people’s business
- 彼は誰とでもやりたがる -> He wants to have sex with anybody
- 彼は人助けをしたがっている振りをしているだけだ -> He is just pretending that he wants to help others
Because of this, when the goal is legitimate, respectable, noble and etc., usually たがる won’t be used. See the below comparisons:
- 彼女は医者になりたいと思っている -> She wants to be a doctor
彼女は医者になりたがっている
- 彼女は貧しい人々を助けたいと思っている -> She wants to help poor people
彼女は貧しい人々を助けたがっている
たがる is not used for simple wishes and/or requests of third parties either.
- 彼はワインが飲みたいって言ってたよ -> He said he wanted to have some wine
彼はワインを飲みたがってたよ
In polite languages, 希望する is usually used instead of たい (たがる is out of question).
- 返金を御希望される場合はその旨お伝え下さい -> Please let us know when you’d like to receive a refund