Mathematics understood through poems? Along with Diophantus mathematics has been represented in form of poems often times. Bhaskara II composes in Lilavati:
Whilst making love a necklace broke.
A row of pearls mislaid.
One sixth fell to the floor.
One fifth upon the bed.
The young woman saved one third of them.
One tenth were caught by her lover.
If six pearls remained upon the string
How many pearls were there altogether?
Or to cite from modern examples: Poetry inspired by mathematics which includes Tom Apostol's Where are the zeros of Zeta of s? to be sung to to the tune of "Sweet Betsy from Pike". Or Tom Lehrer's derivative poem here.
Thus my motivation is to compile here a collection of poems that explain relatively obscure concepts. Rap culture welcome but only if it includes homological algebra or similar theory. (Please let us not degenerate it to memes...). Let us restrict it to only one poem by answer so as to others can vote on the richness of the concept.

To the tune of "The Barney Song/I Love You, You Love Me" (for an earlier generation, "This Old Man"):

vee dee-yoo (plus) 
  yoo dee-vee ... 
  That's the "dee" of "yoo-times-vee". 
  So, remember when the 
  Product Rule you do:
  DON'T you say, 
  "dee-vee dee-you"!

See here.
(c) Copyright, me!
