on/in/at the corner — street corner vs room corner (GiU Unit 124)

The frame

Where is the woman standing? — On the corner. ✓ (she stands on the sidewalk where two streets meet — the street corner)

The three corners

preposition	kind of corner	example
on the corner	street corner — the outdoor spot where two streets meet	waiting on the corner (of Main St and 1st Ave)
at the corner	the junction treated as a location point (also fine, BrE-friendly)	meet me at the corner of the two streets
in the corner	room corner — inside, where two walls meet	sitting in the corner of the room

Two different corners: outdoor street corner → on (or at). Indoor room corner → in.

Why on for streets

The street surface is treated as a plane you stand on (same on-logic as on Broadway, on the pavement, on the corner): the corner is a point on that plane. Inside a room you’re in a 3-D space, so the walls’ meeting point takes in.

Test

Outdoors, at a street junction? → on/at. Indoors, meeting of two walls? → in.

Source

Raymond Murphy, English Grammar in Use, Unit 124 — in, at, on (position) 2. Ebot lesson 2026-09-05.