You use whereas to introduce a comment which contrasts with what is said in the main clause. (表示对比)但是，然而；
Some of the studies show positive results, whereas others do not.
Pensions are linked to inflation, whereas they should be linked to the cost of living…
养老金与通货膨胀挂钩，然而它们其实应该和生活费用挂钩。
Whereas the population of working age increased by 1 million between 1981 and 1986, today it is barely growing.
1981年到1986年间适龄工作人口增长了100万，而现如今该人口数却几乎没有增长。