<P> A phoneme is a sound or a group of different sounds perceived to have the same function by speakers of the language or dialect in question . An example is the English phoneme / k /, which occurs in words such as cat, kit, scat, skit . Although most native speakers do not notice this, in most English dialects the "c / k" sounds in these words are not identical: in kit (help info) (khɪt) the sound is aspirated, while in skill (help info) (skɪl) it is unaspirated . The words therefore contain different speech sounds, or phones, transcribed (kh) for the aspirated form, (k) for the unaspirated one . These different sounds are nonetheless considered to belong to the same phoneme, because if a speaker used one instead of the other, the meaning of the word would not change: using the aspirated form (kh) in skill might sound odd, but the word would still be recognized . By contrast, some other sounds would cause a change in meaning if substituted: for example, substitution of the sound (t) would produce the different word still, and that sound must therefore be considered to represent a different phoneme (the phoneme / t /). </P> <P> The above shows that in English (k) and (kh) are allophones of a single phoneme / k / . In some languages, however, (kh) and (k) are perceived by native speakers as different sounds, and substituting one for the other can change the meaning of a word; this means that in those languages, the two sounds represent different phonemes . For example, in Icelandic, (kh) is the first sound of kátur meaning "cheerful", while (k) is the first sound of gátur meaning "riddles". Icelandic therefore has two separate phonemes / kh / and / k / . </P> <P> A pair of words like kátur and gátur (above) that differ only in one phone is called a minimal pair for the two alternative phones in question (in this case, (kh) and (k)). The existence of minimal pairs is a common test to decide whether two phones represent different phonemes or are allophones of the same phoneme . To take another example, the minimal pair tip and dip illustrates that in English, (t) and (d) belong to separate phonemes, / t / and / d /; since these two words have different meanings, English speakers must be conscious of the distinction between the two sounds . In other languages, though, including Korean, even though both sounds (t) and (d) occur, no such minimal pair exists . The lack of minimal pairs distinguishing (t) and (d) in Korean provides evidence that in this language they are allophones of a single phoneme / t / . The word / tata / is pronounced (tada), for example . That is, when they hear this word, Korean speakers perceive the same sound in both the beginning and middle of the word, whereas an English speaker would perceive different sounds in these two locations . Signed languages, such as American Sign Language (ASL), also have minimal pairs, differing only in (exactly) one of the signs' parameters: handshape, movement, location, palm orientation, and non-manual signal or marker . A minimal pair may exist in the signed language if the basic sign stays the same but one of these parameters changes . </P> <P> However, the absence of minimal pairs for a given pair of phones does not always mean that they belong to the same phoneme: they may be too dissimilar phonetically for it to be likely that speakers perceive them as the same sound . For example, English has no minimal pair for the sounds (h) (as in hat) and (ŋ) (as in bang), and the fact that they can be shown to be in complementary distribution could be used to argue for their being allophones of the same phoneme . However, they are so dissimilar phonetically that they are considered separate phonemes . </P>

A phonetic inventory is determined by identification of minimal pairs