For physical strength:
* ἰσχυρός (iskhuros): This is the most common word for physical strength, meaning "strong, powerful, mighty."
For other types of strength:
* δυνατός (dynatos): This word means "powerful, able, strong," and can also refer to mental or moral strength.
* ἀνδρεῖος (andreios): This word means "brave, courageous," and is often used to describe a strong character.
The best translation depends on the specific nuance you want to convey.