投函
Conjugation
| Affirmative | Negative | |
|---|---|---|
| Present | 投函する | 投函しない |
| Present polite | 投函します | 投函しません |
| Past | 投函した | 投函しなかった |
| Past polite | 投函しました | 投函しませんでした |
| て form | 投函して | 投函しなくて |
| ている present | 投函している | 投函していない |
| ている polite | 投函しています | 投函していません |
| ている past | 投函していた | 投函していなかった |
| ている past polite | 投函していました | 投函していませんでした |
| Conditional ば | 投函すれば | 投函しなければ |
| Conditional たら | 投函したら | 投函しなかったら |
| Volitional | 投函しよう | — |
| Volitional polite | 投函しましょう | — |
| Potential | 投函できる | 投函できない |
| Passive | 投函される | 投函されない |
| Causative | 投函させる | 投函させない |
| Imperative | 投函しろ | 投函するな |
Composed of 投 ('to throw') + 函 ('box'). The character 函 is the same as 箱 ('box') and is the formal Sino-Japanese reading. Literally 'to throw into a box'.
Usage
投函 is the standard, slightly formal word used in postal contexts and on instructions for mail and applications. It is the word the Japanese postal service (日本郵便) uses on its signs and notices, and it is what application forms instruct you to do. In casual speech, Japanese speakers often instead say ポストに入れる ('to put in the mailbox') or 手紙を出す ('to send a letter').
Used both as a plain noun and as a する-verb: 投函する 'to mail, to post (something)'.
Common patterns
Transitive in its する-verb form. The thing being mailed is marked with を, and the location with に:
- 手紙をポストに投函する: to drop a letter in the mailbox
- The passive 投函される is also common in postal-service notices.
Common collocations
- 手紙を投函する: to mail a letter
- 葉書を投函する: to mail a postcard
- ポストに投函する: to drop into a mailbox
- 投票用紙を投函する: to drop a ballot into the ballot box
- 投函日: posting date, mailing date
- 投函時: at the time of mailing
- 投函口: mail slot, drop-off slot (the opening of the box)
- 投函完了: 'mailed' (a status notification)
Similar words
- 手紙を出す: to send a letter — the everyday spoken expression; covers both the act of mailing and the broader act of writing and sending. More casual.
- ポストに入れる: to put in the mailbox — a plain spoken paraphrase of 投函する.
- 郵送: mailing, sending by post — refers to the broader act of sending something through the postal system, including parcels handed over at a post office counter.
- 発送: dispatch, sending out — more general; commonly used by online retailers about shipping orders.
- 差し出す: to send (a letter); to submit — formal verb for handing over or submitting documents.
Register
Formal/written. Common in postal-service signage, instructions on application forms, and news articles. In conversation, native speakers usually prefer the more colloquial 出す or ポストに入れる.