口 (kǒu) ，名 (míng)，位 (wèi)，个 (gè) are all measure words for people, person, so what’s the difference between them? If you don’t have time to read this post, you can just click ‘The Difference Between 口, 名, 位, 个‘ and download as a PDF.
This word is only used in one specific case: to ask how many people are there in a family? it cannot be used in other cases (when it refers to people or person).
Nǐmen jiā yǒu jǐ kǒu rén?
How many people are there in your family?
Wǒmen jiā yǒu wǔ kǒu rén.
There are 5 people in our family.
This word is used to indicate someone’s social status, for example, 「一名学生」yì míng xuésheng – one student，「一名司机」yì míng sījī – one driver，「四名警察」sì míng jǐngchá – four policemen，「几名顾客」jǐ míng gùkè – several customers, etc. Solemn tone, such as 我们厂有五百名工人 wǒmen chuǎng yǒu wǔbǎi míng gōngrén – There are 500 workers in our factory. However, it cannot be used to express the social relationship, such as 「朋友」péngyou – friends,「亲戚」qīnqì – relatives.
A doctor 一名医生 (yì míng yīsheng)
A scholar 一名学者 (yì míng xuézhě)
A teacher 一名老师 (yì míng lǎoshi)
「位」 is usually used to show politesse and respect. Therefore, it is more used in a formal situation or to talk to someone with whom you are not familiar, e.g. 我给你们介绍一下，这位是张先生 (wǒ gěi nǐmen jièshào yíxià, zhè wèi shì Zhāng xiānshēng) – Let me introduce you briefly, this is Mr. Zhang. Besides, when ‘几位’(jǐ wèi), ‘各位’(gè wèi) and ’二位‘ (èr wèi) are used by themselves, it refers to a group of people.
An old person 一位老人 (yí wèi lǎorén)
A professor 一位教授 (yí wèi jiàoshòu)
A Madam 一位女士 (yí wèi nǚshì)
「个」 has a wide use when it is used for people.
wǒ yǒu liǎng gè gēge.
I have two older brothers.
wǒ kànjiàn qiánmiàn yǒu yígè rén.
I saw a person in front of me.
But the tone is very casual, it is more used in a colloquial way. It is not suitable to use it in a formal situation. Moreover, 「个」 can be doubled, such as ‘她们个个都很能干。’ (Tāmen gège dōu hěn néng gàn.) – They are all capable.