form. See formula.
This set of requirements to produce something is the diminutive of L. forma, shape, which directly gives us Eng. form. Hence, also formal, as in evening attire; formality. The format of a book is its shape, from the verb formare, format-, to shape. L. formido, dread, gives us the dreadful, formidable things; whereas something shapely is L. formosa, as the island. Compounds include deform and reformation.
--from Dictionary of Word Origins, by Joseph T. Shipley.
Some friendly synonyms as you begin to think about what forms in poetry might mean:
To Do list