Assonance is the repetition of the vowel sound across words within the lines of the poem creating internal rhymes.
Examples of assonance across words include: crying time; hop-scotch; great flakes; between trees; and, the kind knight rides by.
Look at this stanza from John Agard’s poem 'Hopaloo Kangaroo':
If you can boogaloo
I can do
the boogaloo too
for I’m the boogiest
from The Puffin Book of Fantastic First Poems (Puffin, 2000)
There are examples of the repeated /oo/ sound within the 1st, 4th and 6th lines (assonance), as well as it being used as a rhyme at the end of all the lines, except the 5th line.