Q: I’ve noticed that people have recently begun to pronounce the adjective “alleged” with three syllables, not two. Have you a theory about how this happened, and when? Perhaps the three-syllable pronunciation has been influenced by the four syllables in “allegedly.”
A: The adjective “alleged” can properly be pronounced with either two syllables or three, according to both Merriam-Webster’s Collegiate Dictionary (11th ed.) and The American Heritage Dictionary of the English Language (4th ed.).
So either a-LEJD or a-LEJ-id would be correct. However, this is a relatively recent development.
Our old copy of the unabridged Webster’s New International Dictionary (2nd ed.), printed in 1956, doesn’t even list a separate adjective. It merely lists the two-syllable pronunciation for the past tense and past participle of the verb.
This leads us to believe that the old Webster’s would have regarded the adjectival “alleged” as a participial adjective and would not have given it an extra syllable.
Merriam-Webster’s Dictionary of English Usage (1994) as well as M-W’s updated concise edition (2002) say both pronunciations are acceptable.
But the more conservative Garner’s Modern American Usage (3rd ed.), published in 2009, still recommends two syllables, not three.
Nevertheless, once mainstream dictionaries like American Heritage and M-W’s Collegiate accept a new pronunciation, it has to be regarded as standard English.
As you suggest, it seems likely that the new pronunciation of the adjective was influenced by the four-syllable adverb “allegedly.”