批 pī - measure word

一批 [yī pī], measure word, means a batch or group of people

一批货 [huò] a consignment of goods

一批啤酒 [pí jiǔ] a batch of beer

一批信 [xìn] a batch of letters

一批新书 [xīn shū] a batch of new books

一批鲜花 [xiān huā] a batch of fresh flowers

一批客人 [kè rén] a group of guests

一批新学员 [xīn xué yuán] a new crop of students

一拨 [yī bō], 一帮 [yī bānɡ], 一伙 [yī huǒ], 一批 [yī pī], and 一群 [yī qún] can be used interchangeably when referring to a group of people, though 一群 [yī qún] is more formal than the others. 

一帮 [yī bānɡ] and 一伙[yī huǒ] usually impart a derogatory connotation, for example, 一帮强盗 [yī bānɡ qiánɡ dào, a gang of robbers]; 一伙歹徒 [yī huǒ dǎi tú, a gang of scoundrels]. 一拨 [yī bō] and 一批 [yī pī] are used when referring to a group of people who are taking part in an activity or are on the move, for example, 公司又来了一拨/一批新雇员. [Gōnɡsī yòu láile yī bō / yī pī xīn ɡù yuán.

Another group of new recruits has come to the company.] Of these, only 一拨 [yī bō], 一批 [yī pī] and 一群 [yī qún] can be used to refer to non-human objects. 一拨 [yī bō] and 一群 [yī qún] are used to refer to animals and other non-humans, live organisms, whereas only 一批 [yī pī] is used for non-living things. For example:

河里又来了一群鱼/一拨鱼。[Hé lǐ yòu láile yī qún yú / yī bō yú. There comes another school of fish.]

图书馆来了一批新书。 [Túshūɡuǎn láile yī pī xīnshū. The library has acquired a batch of new books.]