Verse is a writing that uses meter as its primary organisational mode, as opposed to prose, which uses grammatical and discoursal units like sentences and paragraphs. Verse may also use rhyme and other technical devices that are often associated with poetry.
However, while much poetry is written in verse, not all of it is (see prose poetry)
Equally, not all verse is poetry. Generally speaking, what separates the two is that in poetry language achieves the highest possible level of condensation.
In English we speak of "a verse" or "verses," with reference to specific instances, or of "verse," as the general science or art of metrical expression, with its regulations and phenomena.
Roman verse, though essentially the same as Greek verse, was modified by the national development of Italian forms of poetry, by a simplified imitation of Greek measures, and by a varied intensity in the creation of new types of the old Greek artistic forms (Volkmann).
The rules of French verse being, in fact, very severe, and weakness, excess of audacity and negligences of all sorts being very harshly repressed, it is not surprising that, as the personal authority of Hugo declined, various projects were started for lightening the burden of prosodical discipline.