How to say "infiltration" in Japanese

• 潜入せんにゅうJLPT N1approx.Common
  noun, suru verb, intransitive verbCovers physical infiltration: a person sneaking into a building, facility, or organization, or going undercover. Typical in contexts like spies, agents, or journalists infiltrating some place.
  彼かれは農夫のうふに身みをやつして城下町じょうかまちに潜入せんにゅうした。↗

  Disguising himself as a peasant, he crept into the castle town.
• 浸透しんとうCommon
  noun, suru verb, intransitive verbCovers figurative infiltration: ideas, ideology, or culture permeating a group or society, or products penetrating a market. It is not used for a person physically sneaking in.
  日本にっぽんからの輸入ゆにゅう製品せいひんがアメリカの消費者しょうひしゃ市場しじょうに浸透しんとうするには長ながい時間じかんがかかった。↗

  It took a long time for Japanese imports to penetrate the American consumer markets.

Use 潜入 for physical infiltration—people sneaking into places or going undercover—and 浸透 for the figurative spreading or penetration of ideas, ideology, culture, or influence into markets.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 潜入せんにゅうinfiltration
• 浸透しんとうpermeation (of thought, ideology, culture, etc.)
• 浸潤しんじゅんinfiltration (of a liquid)
• 浸出しんしゅつinfiltration
• 浸入しんにゅうinfiltration (e.g. of water)
• 漏入ろうにゅうleaking in