Here's why:
* The schwa sound (ə) is a very common vowel sound in English. It's the sound you make when you're not really emphasizing a vowel.
* In "mama," the first "a" is pronounced with the schwa sound. It's a quick, relaxed sound, similar to the "uh" in "about."
* The second "a" is pronounced with the same sound as the "a" in "father."
So, "mama" is pronounced with the schwa sound in the first syllable, and a different vowel sound in the second syllable.