A simplified procedure for determining whether two sounds represent the same or different phonemes. The cases on the extreme left and extreme right are those in which the sounds are allophones.
phonology, an allophone (/; from the
Greek: ἄλλος, állos, "other" and φωνή, phōnē, "voice, sound") is one of a set of multiple possible spoken sounds (or
phones) or signs used to pronounce a single
phoneme in a particular language.
 For example,
[pʰ] (as in pin) and [p] (as in spin which is less aspirated) are allophones for the phoneme /p/ in the
English language. The specific allophone selected in a given situation is often predictable from the phonetic context (such allophones are called positional variants), but sometimes allophones occur in
free variation. Replacing a sound by another allophone of the same phoneme will usually not change the meaning of a word, although sometimes the result may sound non-native or even unintelligible. Native speakers of a given language usually perceive one phoneme in that language as a single distinctive sound, and are "both unaware of and even shocked by" the allophone variations used to pronounce single phonemes.