The Greek noun Ephesos (Ἔφεσος) is the name of Ephesus, the principal city of the Roman province of Asia (modern western Turkey). It appears about 16 times in Acts and the epistles. Ephesus was home to the temple of Artemis (one of the Seven Wonders), a major harbor, and one of the most important early Christian communities.
Paul spent over two years in Ephesos (Acts 19:10), longer than in any other city during his missionary journeys, resulting in 'all the residents of Asia' hearing the word of the Lord. The church at Ephesus received Paul's letter to the Ephesians, Timothy was stationed there (1 Tim 1:3), and the risen Christ addressed the church at Ephesus first among the seven churches of Revelation (Rev 2:1–7), commending their endurance but warning that they had 'abandoned the love you had at first.'