The noun 西 (xī) means "west" and is used as a directional term. It commonly appears in compound words like 西部 (western part) or 中西部 (midwest). For example, 中西部城镇 means "a midwestern town."
太阳从西边落下去了。
Tàiyáng cóng xībiān luò xiàqù le.
The sun set in the west.
我家在城市的西边。
Wǒ jiā zài chéngshì de xībiān.
My home is on the west side of the city.
他们打算去中国的西部旅行。
Tāmen dǎsuàn qù Zhōngguó de xībù lǚxíng.
They plan to travel to western China.