SUNDAY
The day of the week on which the Lord was resurrected, the first day of the week, the day of the Lord cited in Rev. 1:10: John was in the Spirit on the day of the Lord.
Being the day of the resurrection, it is emphatically the peculiar day of the Christian. Being the first day of the week, it is also suggestive of the beginning of a new order of things, totally different from those related to the legal Sabbath.
It was the day on which the disciples commonly gathered together for the express purpose of breaking bread (Acts 20:7); and although no command is given about it, it is a day especially considered by believers.
It is literally the “Sunday day,” “kuriakos,” a word that occurs only in reference to “the Lord’s Supper” in 1 Cor. 11:20 and to “the Lord’s Day.” It should not be confused with “the day of the Lord” in its eschatological conception, “hëmera kuriou.” (See JEHOVAH’S DAY).
For an in-depth consideration of the subject of the transition from Saturday to Sunday and their respective natures