Final answer:
Irregular forms or free verse are types of poetry without fixed meter or rhyme, offering poets a more flexible structure than forms like sonnets or haikus, relying on thematic and syntactic elements for coherence.
Step-by-step explanation:
The types of poetry that lack strict structure, fixed meter or rhyme scheme are commonly referred to as irregular forms or free verse. Unlike a Sonnet, which has a strict rhyme scheme and structure, a Haiku that does not rhyme but follows a syllabic pattern, or a Limerick that has a playful rhythm and rhyming scheme, free verse poetry does not adhere to regularized meter or rhyme. It leverages other elements like thematic, syntactic, or semantic repetition to create coherence within the poem.
For instance, a free verse poem may use repeated imagery or variations in the syntactic patterns to maintain the poem's structure. Although free verse may incorporate metrical patterns or occasional rhyme, it does not do so in a systematic or patterned manner as seen in more traditional forms such as sonnets or villanelles. Instead, the free verse form is often chosen by contemporary poets for its flexibility and the creative freedom it allows.