件 jiàn - measure word

一件 [yī jiàn], a measure word, used before a piece of clothing; work and a matter; or individual things.

一件: used before a piece of clothing

一件衣服 [yī fú] a piece of clothing

一件背心 [bèi xīn] an undershirt

一件衬衫 [chèn shān] a shirt

一件羽绒服 [yǔ rónɡ fú] a down coat

一件上衣 [shànɡ yī] a jacket

一件T恤衫 [tī xù shān ] a T-shirt

一件: used before a work, a matter

一件工作 [ɡōnɡ zuò] a piece of work

一件事情 [shì qínɡ] a matter

一件: used before some individual things

一件文物 [wén wù] a historical relic or antique

一件行李 [xínɡ li] a piece of baggage or luggage

一件艺术品 [yì shù pǐn] a work of art

一件邮包 [yóu bāo] a postal parcel

一件 [yī jiàn], 一起 [yī qǐ], 一桩 [yī zhuānɡ], and 一宗 [yī zōnɡ] can all be used for a legal case and are interchangeable when referring to a legal case. 

一件 [yī jiàn] is also used for a thing (东西 [dōnɡ xi]), a matter (事情 [shì qínɡ]), an errand (差事[chāi shi]), an accident (事故 [shì ɡù]), and a document (文件 [wén jiàn]). 

In addition to a legal case, 一起 [yī qǐ] is used mainly for an accident (事故 [shì ɡù]), whereas 一宗 [yī zōnɡ] and 一桩 [yī zhuānɡ], which are exactly the same in usage, can also be used for a deal (交易 [jiāo yì]) or a transaction (买卖 [mǎi mài]).