Gwawdodyn Byr is a Welsh meter based on quatrains that is nearly, but not quite, isosyllabic. It features two nine-syllable lines followed by two ten-syllable lines, with a single rhyme sound that appears on all four lines. The sound appears at the end of lines one, two, and four, but in the middle of line three.
An Englyn is one of several types of short poems from Wales. They feature combinations of a ten-syllable line, a short line (five or six syllables), and one or more seven-syllable lines, along with rhymes. Sometimes the entire poem is isosyllabic, featuring only seven-syllable lines.
The Gwawdodyn verse form is the 20th of the codified Welsh meters. This form is made up of quatrains comprised of distinct couplet forms that are, themselves, other members of the codified meters. More specifically, a Gwawdodyn verse will be a Cyhydedd Naw Ban couplet followed by either a Toddaid or a Cyhydedd Hir.
The toddaid is one of the 24 codified Welsh meters. This particular poem form consists of uneven couplets with lines of ten and nine syllables, featuring unusual rhyme schemes that utilize a technique called gair cyrch, ultimately resulting in staggered rhymes that feel exotic to English readers and writers.
Cyhydedd hir is a 19-syllable Welsh verse form that utilizes several rhymes within a very tight space. The verse is ultimately split into four units of 5/5/5/4 syllables, with a rhyme at the end of each unit. The first three units rhyme with each other while the last rhyme sets up the next verse.
A cyhydedd fer is a rhymed couplet consisting of eight-syllable lines with an AA rhyme scheme. This simple format is one of the 24 codified Welsh meters, being both an independent meter and a component used in some of the other Welsh meters.
Byr a Thoddaid is a traditional Welsh form consisting of rhymed quatrains. The form utilizes one symmetrical couplet with eight syllables on each line and one asymmetrical couplet with ten and six syllables, though the order that which the two couplets can appear may differ.