This is the 3177th most frequent Russian word.
молоко
Milk.
Here, 'молока' is used in its genitive singular case, indicating 'a glass of milk'.
Я выпил стакан молока.
I drank a glass of milk.
In this sentence, 'молоко' is in its nominative singular case, functioning as the main subject of the sentence.
Молоко полезно для здоровья.
Milk is healthy for you.
In this example, 'молока' appears in its genitive singular case again, which is commonly used in the context of partitive usage, as in 'some milk'.