Breakdown of Пускай дедушке восемьдесят лет, но он всё же сильный.
он
he / it (for a masculine noun) / it (for a neuter noun)
дедушка
grandfather
год
year
но
but
Questions & Answers about Пускай дедушке восемьдесят лет, но он всё же сильный.
I know пускай usually means "let" (like "let him go"). How does it mean "granted that" here?
In this sentence, пускай is used as a concessive conjunction rather than a command. When it introduces an accepted fact that is immediately followed by a contrasting statement using но (but) or всё же (nevertheless), it shifts meaning to "granted that," "even if," or "even though."
Could I use пусть instead of пускай here?
Yes, absolutely. Пусть and пускай are interchangeable in this type of concessive clause. Пускай is just slightly more colloquial, but both are very common and mean the exact same thing here.
Why do we use both но and всё же in the second half of the sentence?
You could legally use just но (but) or just всё же (still / nevertheless) on its own, but combining them is extremely common in Russian to make the contrast punchier. Но он всё же сильный heavily emphasizes "but nevertheless he is strong."
Quick refresher: why is it дедушке (Dative) instead of the Nominative дедушка?
In Russian, age is always expressed using the Dative case for the person or thing whose age is being stated. Literally, the first clause is structured as "Granted that to grandfather is eighty years."