1Paul, Silvanus, and Timothy, to the assembly of the Thessalonians in God the Father and the Lord Jesus Christ: Grace to you and peace from God our Father and the Lord Jesus Christ.
2We always give thanks to God for all of you, mentioning you in our prayers, 3remembering without ceasing your work of faith and labor of love and perseverance of hope in our Lord Jesus Christ, before our God and Father. 4We know, brothers loved by God, that you are chosen, 5and that our Good News came to you not in word only, but also in power, and in the Holy Spirit and with much assurance. You know what kind of men we showed ourselves to be among you for your sake. 6You became imitators of us and of the Lord, having received the word in much affliction, with joy of the Holy Spirit, 7so that you became an example to all who believe in Macedonia and in Achaia. 8For from you the word of the Lord has been declared, not only in Macedonia and Achaia, but also in every place your faith toward God has gone out, so that we need not to say anything. 9For they themselves report concerning us what kind of a reception we had from you, and how you turned to God from idols to serve a living and true God, 10and to wait for his Son from heaven, whom he raised from the dead: Jesus, who delivers us from the wrath to come.
Church (Gk. ἐκκλησία, ekklesia). (9; Matt 16:18; 18:17; Acts 8:1, Eph 1:22, Rev 1:4, 11, 20; 2:1) Strong’s 1577
The word church [1] is used one hundred fourteen times in the NT. It is formed from the preposition ἐκ (ek), “out of,” and the verb καλέω (kaleo), to “call.” It literally means “those who are called out.” It is used widely in Greek literature to refer to a regularly summoned legislative body, a casual gathering, or a congregation with shared beliefs. The word is used in the Greek Old Testament for the Hebrew word קהל (qahal), the congregation of Israel. It is used in one passage in the NT for a gathering other than church, Acts 19:30, 33. The typical use in the NT is to refer to a local church, that is, a particular body of believers (Rom 16:1; 2 Cor 1:1Gal 1:22; 1 Thess 1:1). This word is also used to refer to the universal church, that is, all true Christians (believers in Jesus Christ) from the Day of Pentecost until the rapture (Acts 12:1; Col 1:18). It is important to note that from the perspective of the NT, the word “church” [1] only ever refers to the people of God and their assembly. Even though modern Christians use it to refer to the “church” building, it is never used this way in the NT. To think and speak biblically about “church” is to think and speak about saved people universally, or a congregation of believers committed to one another and who assemble regularly. In NT thought, the assembly of God’s people is a powerful and unique expression of the presence of God (Eph 2:21). The church is never mentioned in the OT, with its first mention in the Bible in Matt 16:18.
[1] The origin of the English word "church" is from the Middle English word chirche, from Old English cirice, (https://www.merriam-webster.com/dictionary/church) and is related to the German word Kirche, and from the Greek word kuriakon κυριακός, η, ον, "those belonging to the Lord." BAG, p. 459.