This is the 770th most frequent Russian word.
ты
"You" (informal, singular).
The word 'ты' is used here as the second person singular pronoun to address one person casually, indicating familiarity or informal interaction.
Ты знаешь, как добраться до центра города?
Do you know how to get to the city center?
'Ты' is used to address an individual personally in a conversational tone, with a predicate matching this singular subject.
Если ты устал, ты можешь отдохнуть.
If you are tired, you can take a rest.
In this sentence, 'ты' functions as the subject of the subordinate clause, showing the statement's focus on a second person singular subject.