Boyd’s Bible Dictionary:
Capital of Lydia in Asia Minor
Once noted for beauty and wealth; now the miserable village of Sert-Kalessi (Rev. 3:1-6). It was the residence of Croesus, renowned for riches, and Cyrus, when he conquered it, B. C. 548, is said to have captured fabulous treasure there. Alexander captured it from the Persians, and it was again sacked and captured by Antiochus, B. C. 214. It was destroyed by an earthquake. A. D. 17, but was speedily rebuilt. The art of wool-dyeing was discovered there. Seat of one of the seven churches of Asia (Rev. 3:1).
Concise Bible Dictionary:
The capital of ancient Lydia in Asia Minor. The church that was gathered there is known only by being selected as one of the seven typical churches to which addresses were sent by the apostle John (Rev. 1:11; Rev. 3:1,4); See REVELATION. In the time of Croesus, its last king, Sardis was a rich and splendid city. It was taken by Cyrus. Now there is nothing but ruins. Its modern name is Sart, 38° 28' N, 28° 4' E.
Strong’s Dictionary of Greek Words:
Meaning:
plural of uncertain derivation; Sardis, a place in Asia Minor
Jackson’s Dictionary of Scripture Proper Names:
red ones (?)
Potts’ Bible Proper Names:
The remainder; prince of joy; the sun:―capital of Lydia in Asia Minor, Rev. 3:1. {Reliquiae}