成 means 'to become' or 'to complete', and 熟 means 'cooked', 'familiar', or 'ripe'. Together, 成熟 literally conveys the idea of 'becoming ripe' or 'reaching full development'. As an adjective, it describes people (e.g., emotionally or intellectually mature), fruits (fully ripened), ideas (well-developed), or systems (functioning smoothly). As a verb, it indicates the process of ripening or maturing — for example, fruit maturing on the vine or a person growing into adulthood.

This word is commonly used in both concrete and abstract contexts: agricultural reports may say 'the apples have matured', while psychological discussions might refer to 'emotional maturity'. It carries a positive, neutral-to-formal tone and rarely appears in casual slang. Unlike some English uses of 'mature', 成熟 is seldom used as a noun on its own (e.g., you wouldn’t say *这个成熟很珍贵*); instead, use 成熟度 (degree of maturity) or 成熟性 (maturity) when a noun is needed.