WEAK FORMS OF VOWELS
Vowels in English can appear in stressed and unstressed syllables. When a vowel appears in a stressed syllable, it is pronounced with its strong or full form. However, when vowels appear in unstressed syllables, they are normally neutralized/centralized and adopt a rather weak identity known as the weak form. The weak form of all vowels is /ə/ except for /i:/ and /ɪ/ of which the weak form is /ɪ/. This can be schematically represented as the following:
In morphology, weak forms are those words that are pronounced in an unstressed manner. Many of the most common words in English can come in either a strong or a weak form. The most crucial factors in determining whether a word should be pronounced with a weak vowel or a strong one are (a) the type of the word (i.e., function words versus content words), and (b) the number of syllables that compose the word (i.e., whether the word is mono syllabic, bi-syllabic, or poly-syllabic). A function word is a word that has a grammatical rather than semantic function in the language. In other words, the words which are used to express grammatical relationships among words in a sentence are called function words. Functions words include: conjunctions, articles, pronouns, prepositions and some auxiliary and modal verbs. Content words, on the other hand, are rather encyclopedic than linguistic. That is, those words that have independent encyclopedic meanings of their own, and that can be used independently, are called content words. Content words include: main verbs, adjectives, adverbs, and nouns.
Weak forms are all function words. Generally the strong forms of these words are used (a) when they are being directly quoted, (b) when they are being contrasted or (c) if they appear at the end of a sentence. The pronunciation of a weak form can be so different from the strong form that it is barely recognizable as being the same word. If said in isolation, it would be all but unintelligible. Usually, it is the context that makes it understandable.
It is possible to use only strong forms of vowels in English, and some non native speakers do exactly this. However, it sounds very unnatural to a native speaker and it will also mean that a person who only uses the strong forms of English vowels will have trouble understanding native speakers of English who use the weak form all of the time. The most common weak form examples are introduced as follows:
In traditional phonetics, vowels were named on the basis of such criteria as the relative position of the tongue in the mouth, lip rounding, and length.
As such, the vowel /i:/ would, for example, be considered a high front vowel. Other vowels also received their names in this way:
vertical position + horizontal position + vowel.
