'记忆' (jì yì) is a noun meaning 'memory' — the mental capacity to retain, recall, and recognize past experiences or information. It combines two characters with closely related meanings: '记' (jì) means 'to record', 'to note down', or 'to remember', while '忆' (yì) means 'to recall' or 'to reminisce'. Together, they form a compound that emphasizes both the storage and retrieval aspects of memory — not just passive retention, but active recollection. This word is neutral in register and appears frequently in psychological, educational, and everyday contexts.

Unlike simpler terms like '记性' (jì xing, 'memory capacity' — more colloquial and often referring to short-term recall), '记忆' is formal and abstract, commonly used in written language, academic discussion, and expressions about memory loss, enhancement, or formation (e.g., '长期记忆' — long-term memory). It can function as a subject, object, or modifier in sentences, and often pairs with classifiers like '一段' (a segment of) or '一种' (a type of).