Silva is a poetic form that combines varying line lengths and a mix of heptasyllabic and endecasyllabic verses. This form is notable for its flexibility and musicality, making it particularly well-suited for expressing complex emotions and vivid imagery. In the context of 'En una tempestad' by JosĂ© MarĂa Heredia, the silva is utilized to convey the power and beauty of nature while reflecting the poet's internal struggle against external chaos.