侵入

1. Origins, structure, and basic meaning

• Structure: 侵入 (しんにゅう) is a noun and suru-verb for entering across a boundary, often without permission or against what is wanted.
• Basic usage: It can describe intruding people as well as water or animals entering an area.
  • 窓の隙間から雨水が侵入した。 — Rainwater entered through a gap in the window.
  • 畑への動物の侵入を防ぐ柵を立てた。 — We built a fence to prevent animals from entering the field.

2. Common pitfalls and similar expressions

• Entry and intrusion
  • 進入 can be neutral movement into a route or place, whereas 侵入 strongly suggests crossing a boundary or an unwanted incursion.