The unstressed "o" is pronounced like "a" only when it stands directly before the stressed syllable in a word. In other cases it's pronounced like "schwa".Originally Posted by Звездочёт
"O" is pronounced like "a": товарищ, погода, непорядок, корова, молоко.
"O" is pronounced like "schwa": много, мало, удостоверение, молоко.