Hi Avangi,
it's pretty complicated, I'll try to explain it better. I'll use an equivalent phonetic transcription to avoid IPA, because I heard not everyone can see the symbols.
MW breaks the words into syllables in phonetic transcriptions according to how the words would be pronounced syllable by syllable, unlike many other dictionaries I have seen. Its transcriptions are different from all the others, and they seem much more accurate to me. A little example... Situation:
sich-oo-ay-shun --> American Heritage, Longman Dictionary of C. E., Oxford Advanced Learner D., etc.
sih-chuh-way-shun -> Merriam Webster
I believe MW's transcriptions are more like what a native speaker would say if they had to pronounce words very slowly and break them into basic syllables and sounds.
Let's go on. MW doesn't say
coolish is
cool-ish. It's actually
coo-lish. That's true. When you say
coolish, you don't say
cool and then add
ish. The L would be too dark.
Now, the fact is that I change the pronunciation of
a as in
cat before M, N, and the "NG" sound. I also change it before R. So I say Loss Ehuhn-guh-liss... Pair-ihs...
So the question is: are there any cases where I should not change that vowel? Should I say am-eater or a-meter?
PS: I suspect I shouldn't consider that distinction in MW. I just checked some words, and they say
parrot can be
pair-uht or
pa-rut (ok, I only say
pair-uht), but
Paris is only
pa-ris (???). I say
Pair-is, and it is said that way in the audio clip too. So I guess I should always change the sound of my tense a in front of N, M, NG, and R.
And I just found another two examples: mammal and parametric. MW says
ma-mul and
pa-ruh-meh-trik. Does that mean I should pronounce the
a in
mammal as the one in
cat and not the one in
pam? Does that mean I don't have to say
pair-uh-meh-trik, but I should use the
a in
cat? There you go, these are good examples of what I was asking about.