1.inhabitant n. 居民；指某地的常住居民。:最普通用词，一般指常住居民。
He is an inhabitant of Beijing.
他是北京的居民。
She visited some cities of over three million inhabitants.
她访问了几个居住人口超过300万的城市。
2.citizen n. 市民；公民；指住在某个城镇、城市、国家等的居民，也可指具有某国合法国籍的人。
Most Beijing citizens saw the opening ceremony of the 29th Olympic Games on TV.
多数北京市民在电视上观看了第29届奥运会开幕式。
How many American citizens are now living in China?
现在有多少美国公民住在中国？
The interests of British citizens living abroad are protected by the British Embassy.
侨居国外的英国公民的利益受英国大使馆的保护。
He applied to become an American citizen.
他申请成为美国公民。
Old people are just treated like second-class citizens (= unimportant people).
老年人只被当作二等公民对待。
She's an American citizen but lives in Canada.
她是美国公民,但居住在加拿大。
3.resident n. 居民；房客；指在某地的长期定居者或住户，也可指在某地的临时住客。
a resident of the UK/Australia
英国／澳大利亚居民
The residents of this town are very hospitable.
这个镇子里的居民非常好客。
The local residents were angry at the lack of parking spaces.
当地居民对停车位短缺一事非常恼火。
This hotel offers full-body massage only to its residents.
这家旅馆仅向房客提供全身按摩服务。
The hotel bar was only open to residents (= to people staying at the hotel).
这家旅馆的酒吧只对其住客开放。
There were confrontations between local residents and the police.
当地居民和警察之间有过冲突。
The hotel restaurant is open to non-residents.
旅店的餐馆对外开放。
the town's resident population 镇上的居民
The Office of Residence Life may change the door lock combination at any time at the expense of the resident if it is found that the student has shared the combination with others.
如果发现学生与他人共用门锁组合密码,宿舍生活办公室可随时更换门锁组合密码,费用由学生承担。
高考真题- 2015 天津 阅读A
4.civilian : 指相对于军人或官员的平民百姓。
The bomb killed four soldiers and three civilians.
炸弹炸死4名士兵及3名平民。
He left the army and returned to civilian life.
他从军队退了役，重新过上平民百姓的生活。
5. native : 指土生土长的本地居民以及本地动物。
a native of Monaco
摩纳哥当地人
The red squirrel is a native of Britain.
红松鼠原产于英国。
citizen公民、市民；
resident某地（小地方，如住宅）居民；
inhabitant（大地方、区域，如地球）居民