NATO Phonetic alphabet

Some letters may sound over a radio transmission very similar. To reduce the risk of a misunderstanding, all letters aren't spelled individually, but with a easy to differentiate, pre-determined word. 

This also applies to numbers in a similar fashion:

0: "ZEE-RO"   1: "WUN"   2: "TOO"   3: "TREE"   4: "FOW-ER"   5: "FIFE"   6: "SIX"   7: "SEV-EN"   8: "AIT"   9: "NIN-ER"

Link to the offical NATO Page