Key Difference – Lax vs Tense Vowels
The English language has five vowels: a, e, i, o and u. These vowels have the ability to represent a variety of sounds. English phonology traditionally classifies these vowels into types known as lax and tense. The key difference between lax and tense vowels is that tense vowels are longer than the lax vowels of the same height when all other factors affecting the vowel length remains unchanged.
What are Lax Vowels?
The difference between lax and tense vowels cannot be phonetically well-defined as a single characteristic since this distinction is mainly based on phonotactics (the study of the rules governing the possible phoneme sequences in a language). Therefore, the best way to remember the difference between lax and tense vowels is to learn which vowels can be termed as tense and lax.
The lax vowels in contemporary English include,
- /I/ (as i in bit)
- /e/ (as e in bet)
- /æ/ (as a in bat)
- /U/ (as u in put)
- /ô/ (as au in caught)
The length of a vowel is affected by many factors. However, if all other factors including the height of a vowel remain the same, a lax vowel is shorter than a tense vowel. The muscles of the vocal apparatus are relatively loose when articulating lax vowels.
In addition, lax vowels mostly occur in one syllable words that end in consonants.
Ex: but, rat, big, had, put, hat, cat
What are Tense Vowels?
As explained above, tense vowels are relatively longer than lax novels of the same height when all other factors affecting the vowel length remain the same. For example, /i:/ in we (‘wi: ) is longer than the /ɪ/ in (‘bɪg). Moreover, tense vowels usually occur at the end of one syllable words (open syllable words).
Ex: spa, law, bay, bee, ray, too
Some examples of tense vowels include i, e, o, u, ɔ, and ɑ.
In contrast to the articulation of a lax vowel, the tongue and other parts of the vocal apparatus are relatively tense in the articulation of tense vowels.
What is the difference between Lax and Tense Vowels?
Length:
Lax Vowels: Lax vowels are shorter than tense vowels of the same height.
Tense Vowels: Tense vowels are longer than lax vowels of the same height.
Articulation:
Lax Vowels: The muscles of the vocal apparatus are relatively loose when articulating a lax vowel.
Tense Vowels: The tongue and other parts of the vocal apparatus are relatively tense when articulating a tense vowel.
Occurrence:
Lax Vowels: Lax vowels usually occur in one syllable words that end in consonants.
Tense Vowels: Tense vowels usually occur at the end of one syllable words.
Image Courtesy:
“RP vowel chart (monophthongs)” By Ƶ§œš¹ – self-made, based on charts taken from page 242 of Roach, Peter, “British English: Received Pronunciation” in Journal of the International Phonetic Association (2004) Vol. 34(2): 239-245 (Public Domain) via Commons Wikimedia
You list among the lax vowels: /ô/ (as au in caught)
And you list among words with tense vowels: law
To me, “caught” and “law” have the same vowel sound. My dialect is mostly Chicago/Great Lakes Region with a touch of Northeastern US. I’m not sure if this is relevant, but I retain the cot/caught distinction (i.e., “cot” and “caught” are not homophones for me). To me, the vowel in “caught” and “law” are the same vowel that is in the following words: saw, dawn, paw, dog, log, fog, moss, loss, toss, moth, cloth, walk, talk, fought, bought, sought, laud, Maude, caulk, naught, pause
I checked Collins Dictionary for the British pronunciations of caught and law, since you referenced RP pronunciation above. Collins lists the same vowel sound in the pronunciation guide for law and caught.