Lǎoshī jiǎng le 《Lúnyǔ》 lǐ jǐ gè tōngjiǎzì de yòngfǎ.
The teacher explained the usage of several loan characters in the Analects.
Tips
culture
In pre-Qin and Han classical texts, scribes often wrote a phonetically similar character for the intended word (e.g. 蚤 'flea' borrowed for 早 'early'). Reading classical Chinese in school means learning hundreds of such equivalences. The standard formula is 'X通Y' ('X is used for Y').
usage
Compare with 异体字 (yìtǐzì, variant forms of the same character) and 古今字 (gǔjīnzì, historical vs. modern character pairs). 通假 specifically means two distinct characters swapped based on sound.
