TITLE: Injection vs. Surjection: Mnemonic to remember which is which
QUESTION [15 upvotes]: What are some mnemonics to help one remember that Injection = One-to-one and Surjection = Onto? The only thing I can think of is 1njection = 1-1.

REPLY [2 votes]: The way I remember it is that when you get a flu shot your entire body doesn't turn into a giant flu virus, because the needle is smaller than your arm is. Then you can easily remember surjection as "the other one".
Another one is that in-jections are in-ferior and su-rjections are su-perior.