This type of exercise involving minimal sets also allows us to see that there are definite patterns in the types of sound combinations permitted in a language. In English, the minimal set we have just listed does not include forms such as lig or vig. According to the dictionary, these are not English words, but they could be viewed as possible English words. That is, our phonological knowledge of the pattern of sounds in English words would allow us to treat these forms as acceptable if, at some future time, they came into use. They might, for example, begin as invented abbreviations (I think Bubba is one very ignorant guy. ~ Yeah, he’s a big vig!). Until then, they represent “accidental” gaps in the vocabulary of English.

It is, however, no accident that forms such as [fsɪɡ] or [rnɪɡ] do not exist or are unlikely ever to exist. They have been formed without obeying some constraints on the sequence or position of English phonemes. Such constraints are called the phonotactics (i.e. permitted arrangements of sounds) in a language and are obviously part of every speaker’s phonological knowledge. Because these constraints operate on a unit that is larger than the single segment or phoneme, we have to move on to a consideration of the basic structure of that larger phonological unit called the syllable.