求数学定义翻译（有关arithmetic mean和geometric mean的）
如题,看到arithmetic mean 的英文定义,但不知道中文是什么意思,求翻译.原句如下：
if there is one term falling between two given terms of an arithmetic sequence, it's called arithmetic mean.
另外,还有对应的geometric mean的：
if there is one term falling between two given terms of an geometric sequence, it's called geometric mean.
请知道的人帮忙解答一下,谢谢!
灌水勿答,只会用翻译器的勿答.