In the last chapter, we looked at the basic units that make up the forms of words in spoken language: syllables and the consonants and vowels that combine to form syllables. In this chapter, we will look at various ways in which these units may change. First, a given phoneme may be pronounced differently depending on the phonemes that immediately precede and follow it. Though processes like this seem to originate in making it easier for Speakers to produce sequences of phones, they become conventional. That is, different languages make use of different processes of this sort. These kinds of processes also depend on the formality of language; in casual speech, there are often additional simplifications to the forms. Second, the units of linguistic form obviously change through the course of language learning. A beginning first or second language learner does a poor job of producing and recognizing the units of the target language but gets closer to the capability of a native Speaker/Hearer as learning progresses. Finally, the units of linguistic form change more slowly throughout the entire community of Speakers/Hearers. That is, the phonological conventions that define the forms of any language are not constant. In this chapter, we will also review much of what we've covered concerning linguistic form in the context of different English accents.