英语近义次词区别...请各位帮个忙啊!

occupation：
用以成为某个正常的生活来源的一项活动；行业
An activity that serves as one's regular source of livelihood; a vocation.
职业：用以成为某个正常的生活来源的一项活动；行业
An activity engaged in especially as a means of passing time; an avocation.
副业：尤指以此来消耗时间的一项活动；兼差

business:
职业，行业：一个人所从事的职业、工作或行业，
The occupation, work, or trade in which a person is engaged:
职业，行业：一个人所从事的职业、工作或行业：
the wholesale food business.
食品批发行业
A specific occupation or pursuit:
行业，业务：特殊的职业或工作：
the best designer in the business.
该行业最好的设计师

profession,
是指受过良好严格长期教育才能担任的工作，
An occupation requiring considerable training and specialized study:
职业：需要大量训练和专门学习的行业：
the professions of law, medicine, and engineering.
法律、医学、工程的职业
The body of qualified persons in an occupation or field:
同业，同行：某一职业或领域内有资格的人的整体：
members of the teaching profession.
教师行业的人员

employment
则表示仅受雇佣的关系
The act of employing.