At least four verses? More like at least four lines, and that's just if they're written in a more traditional form. Haikus, Cinquains, and several free-verse poems, for example, are often very short, no more than one verse or stanza, but are still capable of delivering a very strong message. In my opinion, length doesn't matter at all. In poetry, as with most art, the length or size of the work holds no relationship with its quality.

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