subject extent

Some poets change subject matter poem to poem; others change subject matter only after exhausting a series of poems related to a single subject.

end or beginning

Was it the last line of this poem, or the first line of the next?

singular thing

The sonnet is a stand-alone poem. It should never be impressed as a stanza in sequence.

organizing principle

He would spend many hours arranging each poem within a book, but a collected poems by convention is just one book after another in chronological sequence.

at sea

A poem at sea apart from its sequence.