马匹 (mǎpǐ) is a formal noun meaning "horses," used as a collective or formal term for multiple horses. It is more literary than the everyday word 马 (mǎ). It appears in historical, military, and formal contexts.
古代打仗需要大量的马匹。
gǔdài dǎzhàng xūyào dàliàng de mǎpǐ.
In ancient times, fighting wars required a large number of horses.
这个农场养了几十匹马匹。
zhège nóngchǎng yǎngle jǐ shí pǐ mǎpǐ.
This farm raises dozens of horses.
将军检查了所有马匹的状态。
jiāngjūn jiǎnchále suǒyǒu mǎpǐ de zhuàngtài.
The general inspected the condition of all the horses.