concentrationn.
英 kɒns(ə)n'treɪʃ(ə)n | 美 'kɑnsn'treʃən
中文n. 浓度；集中；浓缩；专心；集合
词根词源
concentration (n.)1630s, "action of bringing to a center," noun of action from verb concentrate (v.). Meaning "a mass so collected" is from 1670s; "continuous focus of mental activity" is from 1846.
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