戸外

1. Origins, structure, and basic meaning

• Structure: 戸外, read こがい, combines house or door 戸 with outside 外 to denote the outdoors beyond a building.
• Basic usage: It is a formal way to refer to space outside a building, as in 戸外で食べる.

2. Common pitfalls and similar expressions

• Tone and register
  • It is more literary than 外 and centers on the contrast with indoors, unlike 野外, which more strongly suggests an open outdoor setting.