introduction的复数形式为introductions，introduction为可数名词。例句：She was punctilious in the matter of introductions.她在介绍别人时总是举止得体。
Introduction用法例句
1.The camera has undergone only two minor tweaks since its introduction.
这款相机自推出以来仅进行过两次小的改进。
2.Millions of words have been written about the introduction of the euro.
有关采用欧元的文章数不胜数。
3.I tutored a two-day Introduction to Chairmaking course at the college.
我在那个学院教过为期两天的椅子制作入门课。
4.A prolonged drought had necessitated the introduction of water rationing.
由于持续干旱，有必要对用水实行配给了。
5.the introduction of student loans
学生贷款的推行
不可数的抽象名词
freedom自由
laughter笑
wealth财富
poverty贫困
responsibility责任