city是可数名词。city变复数的话，辅音＋y结尾的单词，改y为i，再加es，也就是cities。
例：These gases pollute the atmosphere of towns and cities.
这些气体污染了城镇的空气。
相关介绍
I don't really like cities ─ give me the countryside every time.
我实在是不喜欢城市，一有机会就让我去乡村吧。
Many young people gravitate to the cities in search of work.
许多年轻人被吸引到城里找工作。
Many younger people are leaving the land to find work in the cities.
许多年轻点的人陆续离开农村到城市去找工作。
Which is the largest city in the world?
世界上最大的城市是哪个？
The new mayor is determined to clean up the city.
新上任的市长决心要整治好这座城市。
