In Russian words, regardless of the number of syllables in them, only one syllable is stressed. The stress may fall on any syllable, so there are Russian words with the stress on the first syllable, there are words with the stress on the second syllable, on the third, the fourth, and so on. In the dictionaries and learning materials stress is indicated with a special symbol over the vowel (а́, у́, etc.).
In real Russian texts, such as books, magazines, newspapers, stress is never shown.
Since it is almost impossible to predict which syllable is stressed in any particular word, it is necessary to memorize the stress when learning a word.
The main feature of Russian pronunciation of the vowels is this: unstressed vowels are articulated weaker than the stressed ones, often turning into a dfifferent sound. The weaker articulation of unstressed vowels is called vowel reduction.
Below is a simplified rule for unstressed vowel reduction.