Learn English – Why are the words “lose” and “choose” written differently and pronounced the same way

Although such variation could be the result of things like when the word was borrowed into the language, this variation is probably due to the prosodic structure of the words; we get different vowel sounds because of the way that stress influences vowel quality in English.

In English, unstressed vowels are generally reduced. Take the word record for example.

• The noun form takes first syllable stress: [ˈrɛ kɚd]. If you aren't familiar with IPA, note in particular the [ɛ] vowel and the [ɚ] r-colored schwa vowel. Schwa (and sometimes [ɪ]) is what often shows up in reduced, unstressed vowels in English. Since stress is on the first syllable, we get the r-colored schwa in the second syllable.

• The verb form takes second syllable stress: [rə ˈkoɹd]. Note that the now-unstressed [ɛ] was reduced to [ə], schwa, while the [ɚ] now retains the full [o] sound (with an [ɹ] "r" after it).

Now for bicycle and unicycle:

• bicycle [ˈbaɪ sɪ kəl] has primary stress on the first syllable. The "cy" syllable is unstressed, and so it is pronounced as a mere [sɪ] (or even [sə] by some). Note that tricycle has the same stress pattern, and has the same vowel.

• unicycle [ˈju nɪ ˌsaɪ kəl], being a longer word, has multiple stressed syllables. Primary stress, again, falls on syllable #1, but the important thing is that secondary stress falls on syllable #3, the "cy" syllable. This means that "cy" is pronounced as a full [saɪ] instead of a reduced [sɪ]. Note that motorcycle has the same stress pattern and, again, same vowel.

The word every started out as a contraction of Old English ǽfre ǽlc (each of a group), and the OED gives many Middle English spellings, such as efrec, which only indicate two syllables. Others, such as æveric, do indicate three. It's hard to tell whether they really pronounced it with three syllables, or whether they were spelling it so as to show the relation to the word ever.

If you look at Shakespeare's sonnets, he invariably pronounces every with two syllables. For example, in

Yet so they mourn, becoming of their woe,
That every tongue says beauty should look so,

if you pronounce every with three syllables, the line doesn't scan.

The two-syllable pronunciation has existed since Middle English. People who pronounce it evry aren't wrong in any sense.

So to answer your question: If it's only two syllables, why?
Because some people have been pronouncing it with two syllables from the time when they shoved the two words ǽfre ǽlc together to get efrec.

The OED gives both the two-syllable and the three-syllable pronunciations, and I certainly think it's acceptable to use either pronunciation in a poem.