When most of us think of short poems with rules governing form and number of syllables, we likely think of haiku. Welsh poetry has its own short form in the englyn (plural englynion). There are eight types of englynion, which you can read about here. The most commonly used is the englyn unodl union-- the straight, one-rhyme englyn. This consists of four lines of ten, six, seven, and seven syllables, respectively. the seventh, eighth, or ninth syllable of the first line introduces the rhyme, which then appears at the end of each successive line.
Like haiku, englynion sometimes offer a seemingly simple image, from which the reader can derive deeper meanings (or not). The following englyn by Walter Davies (Gwallter Mechain, 1761-1849) offers one example:
Y nos dywell yn distewi,-- caddug
Yn cuddio Eryri,
Yr Haul yng ngwely'r heli,
A'r lloer yn ariannu'r lli.
Silence brought by the dark night: Eryryi's
Mountains veiled by mist:
The sun in the bed of brine,
The moon silvering the water.
Howell Elvet Lewis' Gobaith Dibrofiad (Life's Morning) is more direct in its feeling and meaning. Lewis also makes use of internal rhymes-- the "ai" in the second and third lines-- and the near "mirror image" sounds in "blodau" (Welsh for "flower") and "bladur" ("blade") in the fourth line.
GOBAITH DIBROFIAD (LIFE'S MORNING)
Bore oes--O! mor brysur--y gwibia
Gobaith ar ei antur:
Canai lai pe gwelai gur
Y blodau dan y bladur
Life's morning--O, how quickly-- fleets
Hope on its adventure:
It would sing less if it saw the pain
Of the flowers beneath the scythe.
(Welsh originals from the Oxford Book of Welsh Verse; English translations from the Oxford Book of Welsh Verse in English).