Alliteration is the repetition of initial sounds in neighboring words.

Like rhyme, alliteration is a great help to memory.
It is powerful a device that prose has borrowed it.
It is the alliteration which makes us remember such phrases as: "sink or swim," "do or die," "fuss and feathers," "the more the merrier," "watchful waiting," "poor but proud," "hale and hearty," "green as grass," "live and learn," "money makes the mare go."