Here's why:
* Schwa sound: Represented by the symbol ə, it's a very short, unstressed vowel sound. It's often described as the sound in the "a" of "about" or the "e" of "the".
* "Dozen" pronunciation: The stress is on the second syllable, "zen". This means the first syllable, "doz", is unstressed, making the vowel sound a schwa.
So, the word "dozen" is pronounced ˈdʌz.ən.