It is not restricted to 17 syllables either. Oh, so patiently they wait. They may be written in the shape of a Japanese lantern. In this case, the first and last lines need not be synonyms. Some little kitten purrs gently by the fire.
Sleep comes quite easily to a drowsy one.
A sijo is a poem with a specific pattern of syllables. Waiting for a crew to arrive To prepare them for a run Sails will be billowing Wind will carry them all away.