成熟(chéng shú) - mature, ripe, fully developed in Mandarin

成熟 (chéng shú) covers three English words at once. Fruit that is 成熟 is ripe. A person who is 成熟 is grown-up in judgement rather than in years. A plan, a market or a piece of technology that is 成熟 is fully developed and no longer experimental.

It also works as a change of state with 了: 芒果成熟了, the mangoes have ripened; 她成熟了, she has grown up. Its opposite depends on the sense, and the useful one is 不成熟, which of an idea means half-baked and of a person means immature, exactly as in English.

The trap is 熟 on its own, which is a different word and not a shortening. 熟 alone means cooked (肉熟了, the meat is done) or familiar (我跟他很熟, I know him well). A learner who trims 成熟 down to 熟 to save a syllable ends up telling people they are well cooked.