Tense–lax

It is also customary to see another binary grouping between the ‘tense’ and ‘lax’ vowels of English. This issue requires more detailed attention, as we may find different rationales and classifications in different publications. In some manuals, the tense–lax distinction is present to account for two vowels that are otherwise described identically. For example, vowels /i/ and /ɪ/, according to the dimensions discussed above, will both be described as “high, front, unrounded” vowels; the same problem is present with regard to /u/ and /ʊ/, because both are “high, back, rounded”. Similarly, the front and back mid vowels /e, ε/ and /o, ɔ/, if not separated as high-mid and low-mid, will end up being described identically. To solve these problems, tense and lax are introduced; the first member in each of these pairs of vowels is called ‘tense’, because (a) it has a higher tongue position, (b) it has greater duration than its ‘lax’ counterpart, and (c) it requires a greater muscular effort in production (hence the term ‘tense’) than the lax vowel. This phonetic definition, however, is not universally adopted. Rather, one finds a phonologically defined ‘tense–lax’ separation more popular in the literature. This distributionally based classification is more useful, because it divides the vowels into two groups that are distinguished by the environments in which they occur. Also, as we will see later, this division will play an important role in the stress rules of English.

The following describes the tense–lax rationale in terms of the different kinds of syllables in which the vowels can occur. Since all English vowels can occur in closed syllables, this cannot be used as a criterion. However, when we examine the vowels and diphthongs that can occur in stressed open syllables, we find /i, e, ɑ, ɔ, o, u, aɪ, aʊ, ɔɪ/ (tense vowels); /ɪ, ε, æ, ʊ, Λ/ (lax vowels) are absent in such syllables. Another syllable type that is said to favor the occurrence of tense vowels and, thus, generally rejects lax vowels is closed by /ɹ̣/. This, however, is a somewhat complex issue, because the contrasts between the tense vowels and their closest lax counterparts are generally lost before /ɹ̣/ for many speakers of American English. We will have more to say about this later. As for the syllable types that favor the occurrence of the ‘lax’ vowels of English, we can cite the syllables closed by /ʃ/ or by /ŋ/. To summarize the mutually exclusive environments, we can say that ‘tense’ vowels are found in stressed open syllables (and syllables with /ɹ̣/ coda), while ‘lax’ vowels are found in syllables with /ʃ/ or /ŋ/ coda.

This distributionally based phonological classification of tense–lax does come into conflict with the earlier mentioned phonetically based classification. First of all, both /o/ and /ɔ/ are ‘tense’ in the latter classification, while they were separated (‘tense’ for the former, ‘lax’ for the latter) in the phonetic classification. Secondly, there will be a problem with regard to ‘duration’, which the phonetically based criterion focuses on. While it is true that several of the lax vowels (/ɪ, ε, ʊ, v/) are short, /æ/ is not. Indeed, this vowel has equal duration with, or even greater duration than, typically long and tense vowels such as /ɑ, e, o/. We will not go into further details in this introductory text and, following the widespread usage, will utilize the ‘tense’ and ‘lax’ grouping as defined by the occurrences in different syllable types.

Now we can revise the vowel chart and incorporate all that has been said.

Before we examine in detail the different subgroups of vowels and their dialectal variation, we will look at some other characteristics that are relevant to all vowels.