1. 全神贯注;专心;专注
    Concentration on something involves giving all your attention to it.

    e.g. Neal kept interrupting, breaking my concentration...
           尼尔不停地打断我，使得我无法集中注意力。
    e.g. We lacked concentration and it cost us the goal and the game.
           我们注意力不够集中，结果丢了球，输了比赛。

2. 集中;汇集
    A concentration of something is a large amount of it or large numbers of it in a small area.

    e.g. The area has one of the world's greatest concentrations of wildlife...
           这个地区是世界上野生动物最为密集的区域之一。
    e.g. There's been too much concentration of power in the hands of central authorities.
           权力一直过多地集中在中央机构手中。

3. 浓度
    The concentration of a substance is the proportion of essential ingredients or substances in it.

    e.g. pH is a measure of the concentration of free hydrogen atoms in a solution...
           pH值是测试溶液中自由氢原子浓度的单位。
    e.g. The latest data showed that global ozone concentrations had dropped several per cent over the last decade.
           最新数据显示，过去10年来全球臭氧的浓度降低了几个百分点。