A dizain is a poetic form which originated in France in the late-14th to early-15th centuries. The poem has either eight or 10 lines, with either eight or 10 syllables per line. The same number of syllables must be used throughout a dizain. Variations in line length are not allowed within a given poem.
In addition to there being rules regarding the number of syllables and number of lines, a dizain has a specific rhyming pattern.
For the more common 10-line dizain, the rhyming pattern is
a – b – a – b – b – c – c – d – c – d
In the 8-line dizain, the rhyming pattern is
a – b – a – b – c – d – c – d