Knowing the sounds (the phonetic units) of a language is only a small part of phonological knowledge.
In earlier chapter, we discussed speakers knowledge of the arbitrary sound/ meaning units that comprise their vocabulary, the morphemes and words in their mental lexicons. We saw that knowing a word means knowing both its form (its sounds) and its meaning. Most of the words in a language differ both in form and meaning, sometimes by just one sound. The importance of phonology is shown by the fact that one can change one word into another simply by changing one sound.
Consider the forms and meanings of the following English words :
sip
zip
fine
vine
chunk
junk
Each word differs from the other words in both form and meaning. The difference between sip and zip is 'signalled' by the fact that the initial sound of the first word is s [s] and the initial sound if the second word is z [z]. The forms of the two words that is, their sounds are identical except for the initial consonants. [s] ans [z] can therefore distinguish or contrast words. They are distinctive sounds in English. Such distinctive soubds are called phonemes.
We see form the contrast between fine and vine and between chunk and junk that [f], [v], [tʃ], and [dʒ] must also be phonemes in English for the same reason substituting a [v] for [f] or a [tʃ] for [dʒ] produces a different word, a different form with a different meaning.
