A sonnet is an argument with a hinge
Fourteen lines is the easy part. What makes a SONNET a sonnet is the turn — the volta — usually around line nine, where the poem changes direction. The first part sets something up; then it pivots, qualifies, contradicts or answers. The form is a small machine for changing your mind in public.
The two main versions put the hinge in different places. The Italian sort divides eight lines against six, so the turn arrives at the ninth. The English sort, which Shakespeare used, runs three QUATRAIN blocks and then a COUPLET, which pushes the surprise into the last two lines and tends to make it snap shut. Same length, different shape of thought.
The haiku rules are not quite the rules
Every school teaches five, seven, five SYLLABLEs. Japanese haiku are actually counted in *on*, sound units that are shorter than English syllables — the word haiku is two syllables in English and three on in Japanese. Seventeen on is closer to about twelve English syllables, so a strict 5-7-5 English haiku is usually padded.
The parts dropped in translation matter more than the count. A traditional haiku carries a kigo, a season word, and a kireji, a cutting word that splits the poem into two images and leaves the reader to connect them. The whole effect is in that gap. Counting on your fingers is a fine place to start, but the juxtaposition is the craft.
Meter is just the heartbeat written down
METER counts stressed and unstressed syllables. The commonest English pattern is the iamb, a quiet beat followed by a loud one, which is the rhythm of ordinary English words like alarm and today. Five of those per line is iambic pentameter, and that closeness to speech is what keeps so much English poetry from sounding sing-song.
The interesting bit is breaking it. A poem that keeps perfect RHYTHM for ten lines and then stumbles is drawing attention to exactly that spot, and good poets do it on purpose. Free verse abandons the count entirely but keeps the LYRIC pressure — it is not the absence of rules so much as a decision to make them up per poem. A BALLAD, by contrast, keeps its metre strict because it was built to be sung, and the REFRAIN comes back like a chorus.
Simile and metaphor are not the same strength
A SIMILE compares with like or as, and the comparison stays visible as a comparison — the reader is told two things resemble each other. A METAPHOR removes the escape route and declares the thing simply is the other thing. That is why metaphor hits harder and why it is easier to overdo.
Both feed the IMAGERY, which is the general word for the pictures a poem puts in your head. The test is whether you can still see it: a dead metaphor like the foot of the hill has been used so often that nobody pictures a foot, which is how a striking image turns into an ordinary word.
The rest of the toolkit
A LIMERICK is five lines with a bouncing rhythm and a punchline, named after the Irish city for reasons nobody has established. An ODE praises something at length. An ACROSTIC spells a word down the left-hand edge, and is the one form children reliably invent for themselves.
The grid also holds the plumbing: the VERSE, the STANZA that groups lines, the COUPLET and QUATRAIN, the RHYME, the POET and the POEM, and the ANTHOLOGY that collects them — a word that originally meant a gathering of flowers. If it is the people rather than the forms that interest you, our poets page is about the writers themselves.