A dactyl is a type of foot, which is really peculiar because daktulos is Greek for finger.
What sort of foot is a dactyl?
It's the type of foot that goes jogging along through so much verse and lyrics and poetry. This sort of foot consists of a heavy stress, together with the weak stress or stresses (if any) that go with it.
For instance, a line of verse that goes da-DAH, da DAH, da DAH, da DAH (like Wordsworth's I WANdered LONEly AS a CLOUD*) consists of four feet of the sort called, as it happens, iambic. You can have other rhythms, too, like DAH-da, DAH-da (TWINkle, TWINkle...) or DA-diddy, DA-diddy, DA-diddy, DA-diddy.
A DA-diddy. DA-diddy poem is made up of feet called dactyls.
Fate sent me, scared, where the lilies are icy, and
Turned their white faces like ghosts scenting death...
Or, in an example I haven't just cobbled together:
Half a league, half a league,
Half a league onwards
which is the beginning of Tennyson's Charge of the Light Brigade.
Dactyls are a bit sticky to write in English, but were used a lot on Ancient Greek.
How to remember that a dactyl goes DAH-diddy? Well, you just remember the Greek daktulos and look at a finger. You have the heavy joint near your hand, and then two smaller, weaker ones.
Word To Consider Today: dactyl. This word, as you know, comes from the Greek daktulos, which means finger.
*In that example the need of the poem to jog leads most people to stress the word AS, which is ridiculous.