糞

A compound ideograph.

Although it appears to be composed of 米 (rice) and 異, its original structure is:

米 — representing small particles or fragments;

其 — a winnowing basket;

廾 — two hands holding something. This depicts the action of holding a basket and removing debris or waste, originally meaning to clean or remove refuse. Over time, the meaning shifted from waste to be cleaned to specifically excrement.
Semantic development: - removing waste or debris; - waste material; - excrement; manure.

분뇨 (糞尿) — feces and urine; excrement

분변 (糞便) — feces

In modern usage, it can appear in formal, medical, or agricultural contexts, but may sound coarse in casual speech.
Related characters: 便 — excrement; convenience (context-dependent)

尿 — urine

屎 — feces