12. Rhyme :]

Definition: The repetition of vowel sounds and sounds following them in words that are near each other in a poem

Example:
Ten thousand eyes were on him as he rubbed his hands with dirt;
Five thousand tongues applauded when he wiped them on this shirt;
Then while the writhing pitcher ground the ball into his hip,
Defiance gleamed in Casey's eye, a sneer curled Casey's lip.

Significance: Words that rhyme make a poem more intersting and also make it sound more like a song.