Among the very first things you'll actually want to produce in Japanese: "I want to eat," "I want one of those," "I have to go," "you don't have to." None of these are covered by the conjugation guides, and they use their own small patterns.
〜たい — "want to (do)"
Take the ます-stem and add たい. The result behaves like an i-adjective, so it conjugates: 食べたい → 食べたかった (wanted to) → 食べたくない (don't want to). The object often switches from を to が: 水が飲みたい.
| Japanese | Reading | Meaning |
|---|---|---|
| 日本に行きたい | nihon ni ikitai | I want to go to Japan |
| 何が食べたいですか | nani ga tabetai desu ka | What do you want to eat? |
| 昨日は休みたかった | kinō wa yasumitakatta | I wanted to rest yesterday |
ほしい — "want (a thing)"
For wanting a noun rather than an action: Xがほしい. Also an i-adjective (ほしかった, ほしくない). Combined with a te-form, 〜てほしい means "want someone to do" — the someone is marked with に: 来てほしい, 手伝ってほしい.
"Have to / must"
There's no single word for "must." Japanese builds it as a double negative: literally "if you don't do X, it won't do." That yields a family of equivalents — formal to casual:
| Pattern | Register | Example |
|---|---|---|
| 〜なければならない | formal / written | 行かなければならない |
| 〜なければいけない | neutral | 行かなければいけない |
| 〜ないといけない | conversational | 行かないといけない |
| 〜なきゃ / 〜なくちゃ | casual (clipped) | 行かなきゃ |
They all mean the same "have to." Pick one — 〜なきゃ for speech, 〜なければいけない for writing — and just recognize the others.
"Don't have to" and "should"
"Don't have to" is 〜なくてもいい ("it's fine even if you don't"). Don't confuse it with prohibition 〜てはいけない ("must not") from the Te-form guide — lack of obligation is very different from a ban. For advice, "should / had better" is 〜ほうがいい — usually the past form 〜たほうがいい when recommending an action (休んだほうがいい, "you'd better rest"). Stronger "ought to" is 〜べき.