The indoor temperature is much higher than outdoors.
Tips
usage
內 is the traditional form; the simplified form is 内. Both are pronounced nèi. In modern simplified Chinese text, 内 and 內 are used interchangeably, but 內 is more common in Traditional Chinese contexts (Taiwan, Hong Kong).
Inside 入 — pictograph of an arrowhead or wedge pointing downward, the indexing radical. With the frame outside and "enter" inside, the compound-ideograph reads "having entered the borders" — i.e. inside. The simplified 内 substitutes 人 for 入.
Outer down-box frame 冂 — represents a boundary or borders of a space. Distinct from 囗 (full enclosure) — 冂 is open at the bottom. Here it sets up the spatial frame: the outer container, the walls of a building or vessel.