In the phrase:
Что э́то?(meaning “What is this?”), the letter о sounds like o in open. But in the second word, the same letter has a sound somewhere between the u in cup and the a in aha. Why? It’s a matter of stress.
When we talk about a stressed syllable, we mean the syllable that gets the most emphasis when you pronounce it.
In the English words below, the stressed syllable is shown bold and colored:
Look at these two English words with the stress on different syllables.
desert meaning “large dry area with sand”When you pronounce them, you’ll notice that the first e changes its sound depending on whether it's stressed or not.
dessert meaning “sweet yummy thing you eat at the end of a meal”
The Russian letter о also changes its pronunciation depending on stress. Here’s the rule: