1. geometric mean

等比中项

2. ethnicity

the fact that someone belongs to a particular ethnic group.

e.g. He said his ethnicity had not been important to him

3. curtail

If you curtail something, you reduce or limit it.

e.g. I told Louie that old age would curtail her activities in time.

4. polygraph

A polygraph test is a test which is used by the police to try to find out whether someone is telling truth.

e.g. Hill's lawyers announced she had taken and passed a polygraph test.

5. supersede

If someone is superseded by something newer, it is replaced because it has become old-fashioned or unacceptable.

e.g. Hand tools are relics of the past that have now been superseded by the machine.

6. canon 

a canon of texts is a list of them that is accepted as genuine or important.

e.g. ' Wuthering Heights' is a central book in the canon of English literature.