This poetry form comes from the Welsh, there are various forms, some with three lines and others with four. The specific form I wish to example here is the straight one-rhyme Englyn or The Englyn Unodl Union. There are four lines in this version which follow a syllable beat per line of 10, 6, 7, 7. The rhyme occurs for the first time in the sixth or seventh syllable in the first line, and then in the final syllable of the remaining three lines. In addition the second line must end with an unstressed syllable and in the last couplet one line-end syllable is stressed and the other line-end syllable is unstressed.
Other rules come into play if a series of Englyns are put together, but the example I have written is merely four lines.
Retired
Cruelly our memory ties youth’s desires
amongst our aging sighs
if lust should lift its head high
would response then petrify?