1. 第二位的;次要的;从属的
    If you describe something as secondary, you mean that it is less important than something else.

    e.g. The street erupted in a huge explosion, with secondary explosions in the adjoining buildings...
           街上发生了剧烈爆炸，邻近的建筑里也发生了程度较轻的爆炸。
    e.g. They argue that human rights considerations are now of only secondary importance...
           他们认为人权方面的考虑现在只是第二位的。

2. (疾病、感染)继发性的，第二期的
    Secondary diseases or infections happen as a result of another disease or infection that has already happened.

    e.g. He had kidney cancer, with secondary tumours in the brain and lungs.
           他患有肾癌，还有脑部和肺部的继发性肿瘤。

3. (教育)中等的，中学的
    Secondary education is given to pupils between the ages of 11 or 12 and 17 or 18.

    e.g. Examinations for the GCSE are taken after about five years of secondary education.
           在接受中等教育约5年后便可参加普通中等教育证书的考试。