The word able is pronounced /'eɪbəl/ or /'eɪbl̩/. The difference in transcription is just a matter of how we treat the syllabic allophone of /l/, i.e. whether we write the schwa /ə/ symbol or a stroke under the /l/. Some sources regard this unstressed vowel as /ʊ/. The diphthong /eɪ/ occurs in words like table, cable, fable and the name Mabel.
By contrast, the suffix -able does not have a stressed vowel at all and is pronounced /-əbəl/ or /-əbl̩/. Many foreign speakers of English stress the suffix unnecessarily, which can make the word impossible for listeners to understand. Anecdotal examples include a Polish speaker of English pronouncing comfortable as come for table.
The suffix -ible has same pronunciation as -able.
Ex. 1 Put the following words containing -able in two categories: a. with a stressed sound /eɪ/ or b. with the unstressed /ə/. Which syllable carries primary stress?
preferable, publishable, vegetable, stable, unstable, capable, comfortable, drinkable, portable, irreconcilable, indescribable, unfathomable, unbreakable, sable, remarkable
Ex. 2 Do the following words contain -able or -ible?
leg__ble, illeg__ble, ed__ble, imagin__ble, ined__ble, respons__ble, permiss__ble, inflamm__ble
KEY
1. a. stable - 1st, unstable - 2nd, sable - 1st
b. preferable, publishable, vegetable, capable, comfortable, drinkable, portable - 1st, irreconcilable - 4th, indescribable - 3rd, unfathomable, unbreakable, remarkable - 2nd
2. Inflammable and imaginable have "a"; all the other words have "i"
