Why do JLPT N1 learners confuse 退化 with 込める?

Both words occupy adjacent semantic territory, which is exactly why the JLPT uses them as distractors for each other on multiple-choice items. The fastest way to stop confusing them is to study them as a pair, write a one-sentence contrast in your own words, and drill the pair specifically rather than each word in isolation.

Is 退化 or 込める more common on JLPT N1?

Both appear in the JLPT N1 curriculum and either may show up on a given exam. Don't try to predict which one the test will choose — learn to distinguish them and you'll be safe regardless. Both belong to the General Verbs (9) theme of N1 vocabulary.

How do I practice this confusion pair?

Free option: visit /try and pick a confusion drill. Paid option: none — JLPT Mastery is free during launch. Whichever route you take, the engine specifically re-tests pairs you've gotten wrong rather than rotating through general vocabulary review.

JLPT N1 · Advanced · Meaning confusion

退化 vs 込める

Q: What's the difference between 退化 and 込める?

退化 (たいか) means "degeneration, retrogression" and 込める (こめる) means "to include, to put into". Both share the 辶 radical. A learner might confuse "moving backward" (退) with "moving into" (込) if they generalize the movement radical without distinguishing the specific right-hand components like 艮 and 入.

Why JLPT N1 learners mix up 退化 (たいか, “degeneration, retrogression”) and 込める (こめる, “to include, to put into”).

退化

たいか

degeneration, retrogression

verb

込める

こめる

to include, to put into

verb

Theme: General Verbs (9)JLPT N1

Why these get confused

Both share the 辶 radical. A learner might confuse "moving backward" (退) with "moving into" (込) if they generalize the movement radical without distinguishing the specific right-hand components like 艮 and 入.

How to tell them apart

Anchor on the meaning, not the form. 退化 (degeneration, retrogression) and 込める (to include, to put into) live in adjacent semantic territory. Memorize the boundary, not just each word.
Read the example sentences below. Seeing each word in its natural context builds a faster lookup than studying the dictionary form alone.

In a sentence

退化 (degeneration, retrogression)

私が何を言いたいかおわかりでしょう。
私はいたいからここにいるんです。

込める (to include, to put into)

相手のエースを封じ込めれば勝機はある。
彼は力を込めて弓を引いて遠く矢を射ることを試した。

How JLPT tests this pair

On JLPT N1, this pair shows up as a vocabulary meaning question. You see one word and pick its English equivalent from four options — one of which will be the other word in this pair, chosen as a distractor precisely because of the overlap.

Sample item

「退化」の意味は？