〜込む / 〜こむ

into (movement inward) / deeply, thoroughly (intensifies the action)

Verb stem + 込む has two jobs. (1) Movement into something: 飛び込む "jump into", 書き込む "write into", 持ち込む "bring into". (2) Going deep or staying in a state: 考え込む "be lost in thought", 黙り込む "fall silent", 落ち込む "feel down". In both cases the picture is something going inside and settling there.

Very common in everyday verbs; you will meet it in vocabulary and reading rather than as a separate grammar item. Knowing the two senses helps you guess the meaning of new compounds (申し込む, 振り込む, 座り込む).

• Verb ます-stem + 込む (Group 1 verb: 込んだ, 込んで, 込みます)
• Sense 1 (into): 飛び込む, 入り込む, 持ち込む, 書き込む, 押し込む, 申し込む
• Sense 2 (deep / lasting): 考え込む, 黙り込む, 落ち込む, 座り込む, 寝込む, 信じ込む

1. 01

   彼は急いで電車に飛び込んだ。

   かれはいそいででんしゃにとびこんだ。

   He hurriedly jumped into the train.

   Sense 1: jump into the train.

2. 02

   大切なことはノートに書き込んでおく。

   たいせつなことはノートにかきこんでおく。

   I write down important things in my notebook.

   Sense 1: write into the notebook.

3. 03

   彼女はその問題を深く考え込んでいた。

   かのじょはそのもんだいをふかくかんがえこんでいた。

   She was deeply absorbed in thinking about the problem.

   Sense 2: sink deep into thought.

4. 04

   そのニュースを聞いて、彼はすっかり落ち込んでしまった。

   そのニュースをきいて、かれはすっかりおちこんでしまった。

   Hearing that news, he became completely depressed.

   Sense 2: 落ち込む = sink into low spirits.

5. 05

   会場に食べ物を持ち込むことはできません。

   かいじょうにたべものをもちこむことはできません。

   You cannot bring food into the venue.

   Sense 1: 持ち込む = bring in. Common on signs.

• 〜入れる / 〜入る

  Plain 'put in / go in'. 込む adds force or depth (押し込む = shove in).

• 〜きる

  'Completely' about finishing; 込む is about going inside or deep. Compare side by side

• 混む (crowded)

  A separate verb: 電車が混んでいる 'the train is crowded'. Same sound, different kanji and meaning.

• ✗

  電車に飛ぶ込んだ。

  ✓

  電車に飛び込んだ。

  Why

  込む attaches to the ます-stem (飛び).

• ✗

  彼女は深く考え込みました。→ translated as 'she considered it carefully'

  ✓

  考え込む = 'she was lost in thought / brooded'.

  Why

  Sense 2 describes sinking into a state, often with worry, not simply careful consideration.

• ✗

  道が込んでいる (written 込)

  ✓

  道が混んでいる

  Why

  'Crowded' is 混む. The compound suffix is 込む.

Set expressions worth memorising: 申し込む (apply), 振り込む (bank transfer), 思い込む (assume wrongly), 教え込む (drill into someone), 冷え込む (get very cold). The noun form 〜込み appears in 税込み (tax included), 申し込み (application), 見込み (prospect). Many 込む verbs are intransitive (落ち込む, 黙り込む) and take が for the person.