A phonetic alphabet is any of three things:

• A writing system used for transcribing the sounds of human speech into writing. This is a linguistic tool, not a replacement alphabet. Among phonetic alphabets are:
  • The International Phonetic Alphabet
  • SAMPA, an ASCII version
  • X-SAMPA, an extension of SAMPA
  • Kirshenbaum, an ASCII version originally developed for usenet newsgroups
  • The phonetic symbols in Webster's Third New International Dictionary

• A new alphabet for languages which are not phonetic. It would replace the current one (at least for learning a language). For example:
  • Herbert Bayer's fonetik alfabet
  • John Malone's UNIFON
  • Sir James Pitman's ITA, the "initial teaching alphabet"
  • Shavian alphabet, in honor of George Bernard Shaw.
  • Jan Tschichold's alphabet

• A list of standard words used to identify letters in a message transmitted by voice (including over radio, telephone, etc.). Occasionally known as a "radio alphabet". See:
  • NATO phonetic alphabet
  • Joint Army/Navy Phonetic Alphabet
  • RAF phonetic alphabet
  • LAPD phonetic alphabet