“某男””“某女”“某先生”“某学生”“某商贩”“某市长”“某老板”：

1.  用不定冠词 a 表示“某个”：

 "a man", "a woman", "a gentleman", "a student", "a vendor", "a mayor", "a boss"

2.  用 a certain 表示“某个”：

"a certain man", "a certain woman", "a certain gentleman", "a certain student", "a certain vendor", "a certain mayor", "a certain boss"

3.  用 some 表示“某个”（被修饰名词用单数）：

 "some man", " some woman", "some gentleman", " some student", "some vendor", "some mayor", "some boss"