The Kelly lune (after poet Robert Kelly) is a three-line, thirteen-syllable form, with syllable count 5-3-5. Unlike traditional Japanese haiku, nature themes are not required, and simile and metaphor are allowed.
The Collom lune (after poet Jack Collom) is a three-line, eleven-word form, with word count 3-5-3. All themes fine, and simile and metaphor may also be included.
Here is one of each that I posted for today’s Poetic Asides prompt to write about a lightbulb moment (or just a lightbulb):
but why mercury?
(Collom variant )