Wishes
This article covers how to express own or others' wishes using -tai, -tagaru, hoshii, and -te moraitai/-te hoshii.
たい (-tai)
To express one's own wish to do something, add -tai to the infinitive. In normal polite Japanese this is followed by desu. Verbs ending in -tai are treated like -i adjectives, and so have a negative form ending in -taku arimasen and a past form ending in -takatta desu.
Examples:
お茶が飲みたいです。
Ocha ga nomitai desu.
I would like some tea.
昨日休みを取りたかったけど、大変忙しくて、取ることができませんでした。
Kinou yasumi o toritakatta kedo, taihen isogashikute, toru koto ga dekimasen deshita.
I wanted to take yesterday off, but I couldn't because I was extremely busy.
テレビを見たいです。
Terebi o mitai desu.
I want to watch TV.
川で泳ぎたいです。
Kawa de oyogitai desu.
I want to swim in the river.
デートをしたいです。
Deeto o shitai desu.
I want to date.Others' Wishes
-たがる - Other's Wishes
If you are talking about someone else wanting to do something, then you simply replace たい (tai) with the ending たがる (tagaru). For normal polite Japanese, this means that you would replace たいです (tai desu) with たがっています (tagatte imasu), forming continuous form at the same time, to express that the person is wishing it currently。
Examples:
電車で学校に行きたがっています。
Densha de gakkou ni ikitagatte imasu.
He/she wants to go to school by train.
先生はコーヒーを飲みたがっています。
Sensei wa koohii o nomitagatte imasu.
The teacher wants to drink coffee.
田中さんは絵を書きたがっています。
Tanaka-san wa e o kakitagatte imasu.
Mr./Ms. Tanaka wants to draw a picture.
ほしい (hoshii)
To express a desire for a thing, use the -i adjective hoshii. To use the construct with verbs, add ほしい (hoshii) after the -te form of the verb.
Examples:
彼女は、ボーイフレンドがほしいといいました。
Kanojo wa, bouifurendo ga hoshii to iimashita.
She said she wants a boyfriend.
コーヒーが欲しいです。
Koohii ga hoshii desu.
I want a cup of coffee.
てもらいたい (-te moraitai) / てほしい (-te hoshii)
To express a desire for someone to do something, use -te moraitai (-てもらいたい) or -te hoshii (-てほしい) form and the infection of them. When "who" you want to do something is not explicitly stated, it is assumed you want the listener to do the action:
Examples:
コーヒーを飲んでもらいたいです。 / コーヒーを飲んでほしいです。
Koohii o nonde moraitai desu. / Koohii o nonde hoshii desu.
I want you to have a cup of coffee.
電車でそこへ行ってもらいたいです。 / 電車でそこへ行ってほしいです。
Densha de soko e itte moraitai desu. / Densha de soko e itte hoshii desu.
I want you to go there by train.
It is possible to explicitly state "who" you want to do, as follows:
Examples:
あなたにコーヒーを飲んでもらいたいです。 / あなたにコーヒーを飲んでほしいです。
Anata ni koohii o nonde moraitai desu. / Anata ni koohii o nonde hoshii desu.
I want you to have a cup of coffee.
彼に電車でそこへ行ってもらいたいです。 / 彼に電車でそこへ行ってほしいです。
Kare ni densha de soko e itte moraitai desu. / Kare ni densha de soko e itte hoshii desu.
I want him to go there by train.
This page is based on a modified part of "Some Notes on Japanese Grammar" published for your personal use, with the kind permission of Keith Smillie (http://www.cs.ualberta.ca/~smillie/)
It is worth pointing out, however, that for nihonjin, the Romanizations "si" and "ti" are more natural; the system of Romanization in which these choices are made consistently is called "kunreisiki" ( "kunreishiki" ). So what probably happened here is that the roomaji were added by a nihonjin, who forgot that "shi" and "chi" are easier to read for many people, especially English speakers.
"Densha de itte hoshii (desu)"
is
"I want YOU to go by train."
where the person who would act is not specified so it's automatically assumed to be "YOU" (the listener).
If you want to say "I want HIM to go by train.", then,
"Kare ni densha de itte hoshii (desu)."
See also:
http://www.studyjapanese.org/component/fireboard/?func=view&catid=2&id=4770#4770
...or I better write this on the forum perhaps?
Smilie-san was saying that to express a wish for an action to take place, one would use the -te form of a verb followed by hoshii. For example, I believe "densha de itte hoshii desu" would mean "I want to go by train"; I don't know exactly how this would differ from "densha de ikitai desu", but perhaps it puts more emphasis on wanting to go BY TRAIN.