思(おも)い込(こ)む

おもいこむ

godan verb

to be convinced, to assume, to believe firmly

Conjugation

	Affirmative	Negative
Present	思(おも)い込(こ)む	思(おも)い込(こ)まない
Present polite	思(おも)い込(こ)みます	思(おも)い込(こ)みません
Past	思(おも)い込(こ)んだ	思(おも)い込(こ)まなかった
Past polite	思(おも)い込(こ)みました	思(おも)い込(こ)みませんでした
て form	思(おも)い込(こ)んで	思(おも)い込(こ)まなくて
ている present	思(おも)い込(こ)んでいる	思(おも)い込(こ)んでいない
ている polite	思(おも)い込(こ)んでいます	思(おも)い込(こ)んでいません
ている past	思(おも)い込(こ)んでいた	思(おも)い込(こ)んでいなかった
ている past polite	思(おも)い込(こ)んでいました	思(おも)い込(こ)んでいませんでした
Conditional ば	思(おも)い込(こ)めば	思(おも)い込(こ)まなければ
Conditional たら	思(おも)い込(こ)んだら	思(おも)い込(こ)まなかったら
Volitional	思(おも)い込(こ)もう	—
Volitional polite	思(おも)い込(こ)みましょう	—
Potential	思(おも)い込(こ)める	思(おも)い込(こ)めない
Passive	思(おも)い込(こ)まれる	思(おも)い込(こ)まれない
Causative	思(おも)い込(こ)ませる	思(おも)い込(こ)ませない
Imperative	思(おも)い込(こ)め	思(おも)い込(こ)むな

1. to be convinced, to be under the impression

To believe something strongly, often without sufficient evidence or despite being incorrect.

彼(かれ)は正(ただ)しいと思(おも)い込(こ)んでいる。

He's convinced he's right.

彼女(かのじょ)は自分(じぶん)が悪(わる)いと思(おも)い込(こ)んでいた。

She was convinced that she was at fault.

一度(いちど)思(おも)い込(こ)んだら、なかなか考(かんが)えを変(か)えない。

Once he's convinced of something, he won't easily change his mind.

子供(こども)のころ、サンタクロースは本当(ほんとう)にいると思(おも)い込(こ)んでいた。

When I was a child, I was firmly convinced that Santa Claus really existed.

勝手(かって)に思(おも)い込(こ)んでいただけで、事実(じじつ)は違(ちが)った。

I had just assumed it on my own, but the truth was different.

2. to assume mistakenly, to jump to conclusions

To believe something to be true based on assumptions rather than facts.

会議(かいぎ)は来週(らいしゅう)だと思(おも)い込(こ)んでいた。

I was under the impression that the meeting was next week.

思(おも)い込(こ)みが激(はげ)しい人(ひと)だ。

He's a person who jumps to conclusions. / He has strong preconceptions.

[Note: 思(おも)い込(こ)み is the noun form meaning 'preconception' or 'assumption']

道(みち)を間違(まちが)えたのは、右(みぎ)に曲(ま)がると思(おも)い込(こ)んでいたからだ。

I took a wrong turn because I assumed I should turn right.

彼(かれ)が犯人(はんにん)だと思(おも)い込(こ)んでいたが、実(じつ)は無実(むじつ)だった。

I had assumed he was the culprit, but he was actually innocent.

全員(ぜんいん)が賛成(さんせい)していると思(おも)い込(こ)んでいたが、反対(はんたい)の人(ひと)もいた。

I had assumed everyone was in agreement, but there were people opposed as well.

思(おも)い込(こ)む is an intransitive verb (自動詞(じどうし)) meaning to be firmly convinced of something.

COMPOUND STRUCTURE:

思(おも)う (to think) + 込(こ)む (to go into deeply) → to think deeply and become fixed in belief

ASPECT (ている):
思(おも)い込(こ)んでいる is the most common form, indicating a state of being convinced or under an impression.

COMMON PATTERNS:

〜だと思(おも)い込(こ)む (be convinced that~)
思(おも)い込(こ)みが激(はげ)しい (prone to making assumptions)
勝手(かって)に思(おも)い込(こ)む (assume on one's own)

RELATED NOUN:

思(おも)い込(こ)み: preconception, assumption, belief

NUANCE:
Often implies that the belief is mistaken or at least unverified. Used when someone has convinced themselves of something that may not be accurate.

core

Added 2026.1.14 12:52 · Revised 2026.6.2 0:42

04500/04588_omoikomu