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This is a very interesting question, which cuts right to the heart of
the relationship between word formation and pronunciation.
Unfortunately the answer to your question, "Is fire one syllable or
two?" is that it depends on how you pronounce it. This has a lot to do
with the complexities of human speech and vowel formation.
Your question is really asking, "What is a syllable?" For the most
part, our original grammar school understanding that "A syllable is a
part of a word with a single vowel sound" is essentially correct, but
there's more to it than that. Let's look at a linguistic defintion of
" A syllable is a unit of sound composed of -1- a central peak of
sonority (usually a vowel) and -2- the consonants that cluster around
this central peak." (1)
It is important to remember that linguistic definitions of things like
syllables do not depend on the spelling of the word, but rather, the
phonetic makeup of the word. Basically, this definition tells us that
a syllable is a cluster of phonemes -- one of which has the property
of "sonority", essentially "ability to behave like a vowel". Sonority
is a scale: Vowels are most sonorous, less sonorous are laterals (like
/r/ and /l/) and nasals (like /n/ and /m/), less so are fricatives
(/v/, /f/, etc.) and the least sonorous are plosives (/p/, /k/,
In the case of the word "fire," what's happening is this:
If you pronounce the word "fire," you are generally using the
/f/ /ay/ /r/, where /ay/ is a very high vowel that is moving forward
in the mouth (a diphthong-- changing between an /ah/ sound and an /ee/
sound). Suddenly when you're done pronouncing the /ay/, you need to
drop very far back to make the /r/ sound, which originates way back on
the soft palate. Coming off of the diphthong makes a natural break in
the word and /r/ acts as what is knowns as a "syllabic consonant", a
consonant which acts as a syllable indicator. We can be certain that
the /r/ syllable isn't receiving a vowel sound from the diphthong
because the final sound in the diphthong is at the opposite end of the
mouth as the /r/ sound.
Because phonemes like /r/ have such a high sonority, they easily take
on the role of vowels in syllables (depending on the formation of the
word). If you listen very carefully to the word "fire", you will
notice that there is no real separate vowel sound assigned to the
second syllable. Some people would tack a "schwa" (a neutral "uh"
sound, symbolized by an upside-down "e") before the /r/ sound, but
really it's not a separate phoneme: Play the following game: Go "fff,
eye, rrr" and gradually run the sounds together by saying them faster
and faster in sequence. Compare this to trying to run together "fff,
eye, uh, rrr." The first definitely sounds like "fire" (but
notice--only three phonemes) and the second sounds like some
ridiculous thing. Really /r/ is acting as its own vowel.
Similar in behavior is the word "oil", which is composed of two
phonemes: /oy/ (another diphthong) and /l/. But it is still pronounced
by most people as two syllables. Once again we have a diphthong
followed by a consonant with a high sonority. The movement across the
mouth of the diphthong seems to engage the sonorous nature of the /r/.
Also compare the word "pattern" which, despite the vowel appearing in
the second consonant is really pronounced more like /p/ /ae/ /t/ /r/
/n/. (compare "pattern" and "pat-urn"). The plosive /t/ is (through
its non-sonorous contrast) encourages the sonority of /r/ and causes
/r/ to act as a syllabic consonant. (1)
So it would seem that the initial answer to your question above is
that "fire" has two syllables. However, linguistics is not only about
how a particular person pronounces a word but also about any common
pronunciation of the word. It's easy to imagine a person with a
Southern accent saying /f/ /ah/ /r/, which has only one syllable. The
reason is that the diphthong is gone -- the double movement across the
mouth that made /r/ act as a syllabic consonant is gone. Now one could
imagine a less "regional" variation of this occurence by gradually
moving the /ah/ phoneme up in the mouth until the vowel sound is more
forward, but the absence of the diphthong makes the word still sound a
little weird to someone who is used to hearing neutral, "accent-free"
English (e.g., "newscaster English"). If you are willing to accept
widespread regional pronunciations as "standard" then there are
clearly two pronunciations of "fire" in English, one with one syllable
and one with two. But if you wish to avoid such complications and
declare that "standard" means "as spoken by someone with a neutral
accent," then you would be hard-pressed to convince someone that
"fire" could be pronounced with one syllalbe. Unfortunately,
linguistically speaking, what is "standard" is what is spoken. This
sometimes includes multiple pronunciations. Particularly in American
English where there is no national academy to prevent language change
(q.v. France) it is seldom a cut-and-dried decision of what consitutes
"standard" and what does not.
It is worth pointing out that it would be nearly impossible to
genuinely pronounce "fire" with the full /ay/ diphthong without
syllabizing the /r/. In this sense the /f/ /ay/ /r/ pronunciation of
"fire" definitely has two syllables, linguistically speaking.
In light of all the above, the answer to your second question depends
on what you consider standard.
For /f/ /ah/ /r/ or similar, assuming you accept this as a possible
"standard" pronunciation, "fireplace" has two syllables.
For /f/ /ay/ /r/, the word "fireplace" has three syllables. However,
in this case it is a little easier to get away with eliminating the
diphthong /ay/ (replacing it with a central /a/ sound (a little higher
than the "a" in "far")) and not sound too "weird" to neutral ears.
I hope you find this answer satisfying. If anything was unclear to you
or if you are not satisfied by this answer, please request a
clarification before rating and I will clarify the answer to the best
of my abilities.
(1) SIL International Linguistics Page, Glossary of Linguistic Terms
Definitions of many of the other terms used (particularly "syllabic
consonant" but others as well) can be found here.
Google search terms: <syllable linguistics definition>