Long in the tooth means old, ageing, or past youth, originally from the way horses’ teeth appear longer with age. In poetry, the idiom can bring earthy humour to themes of ageing, experience, decline, or seasoned wisdom. It may be affectionate, self-mocking, rude, or elegiac depending on context. A poet might use it to resist sentimental language about age, replacing grandeur with stable-yard realism. It also raises questions about how societies value or dismiss those marked by time.

Long in the tooth means old or ageing, originally from judging a horse’s age by its teeth. In poetry, it can be humorous, affectionate, or dismissive. The phrase brings ageing into the body through visible physical evidence. It suits poems about animals, old soldiers, ageing artists, parents, or the speaker’s own self-mockery. Students should consider tone carefully, since it can sound kindly, comic, or rude depending on context.