language works on sound system and one sound can change the meaning of the entire word. Let's see that the sound of /p/ and the sound of /b/ may have not a big distinct difference with pronounce separately but when the same one is inserted in the wood, it changes the meaning entirely e.g. 'pack' and 'back' There is not a big difference in pronunciation but the meanings are entirely change. This property is called discreteness. Each sound in the language is treated as discrete. It is possible to produce a range of sounds in a continuous stream which are generally like the P and B sounds. These physical different sounds could conceive of as the spoken counterpart of a written set