Lǎoshī ràng wǒmen qūfēn gǔtǐshī hé lǜshī de bùtóng.
The teacher asked us to distinguish old-style verse from regulated verse.
Tips
history
Contrast with 近体诗 (jìntǐshī, 'new-style' regulated verse), which codified strict tonal patterns, parallelism, and line counts starting in the Tang. 古体诗 refers to pre-Tang modes, or Tang-and-later poems that deliberately adopt the freer old form.
usage
Lines in 古体诗 are usually 4, 5, or 7 characters long, but unlike 律诗 the poem can run to any length and doesn't have to follow the 平仄 tone-matching rules.