ESV: "When you come together, it is not the Lord's supper that you eat."
ASV: "When therefore ye assemble yourselves together, it is not possible to eat the Lord’s supper:"
Authorized KJV: "When ye come together therefore into one place, this is not to eat the Lord’s supper."
NWT 2013: "When you come together in one place, it is not really to eat the Lord's Evening Meal."
Bill Mounce on δεῖπνον:
pr. a meal; supper, the principal meal taken in the evening, Lk. 14:12; Jn. 13:2, 4; meton. food, 1 Cor. 11:21; a feast, banquet, Mt. 23:6; Mk. 6:21; 12:39
Mounce's Complete Expository Dictionary: Noun: δεῖπνον (deipnon), GK 1270 (S 1173), 16x. deipnon means “supper, feast, banquet” and refers to the main meal in biblical times, eaten in the evening. This is clear from Lk 14:12, where a separate term is used for a “luncheon,” a meal eaten earlier in the day. deipnon can also refer to a more formal meal or eating occasion, a “banquet.”
The NWT has been criticized for "overtranslating" 1 Cor. 11:20, 25, but is this criticism justified in the light of what δεῖπνον probably means in these verses?
Bowman invokes Anthony Thiselton to undermine the rendering "Evening Meal" as we find in NWT. Thiselton explains that δεῖπνον doesn't necessarily specify the meal's timing, whether it's evening or morning. Let's quote Bowman verbatim as he uses Thiselton:
Thiselton comments that deipnon “usually designates the main meal of the day in the Graeco-Roman world. Like the English dinner, it usually denotes an evening meal in formal circles, but as in the case of the English phrase ‘Christmas dinner’ the emphasis concerns the major event rather than the specific timing. It need not always be an evening meal, although in practice it usually was” (Thiselton, First Epistle to the Corinthians, 863-64). Thus, the rendering “evening meal” in the New World Translation at 1 Corinthians 11:20, 25 is an overtranslation that makes the timing of the meal specific in a way that the Greek wording does not (cf. Mark 6:21; 12:39; Luke 14:12-24; 17:8; Rev. 3:20).
It's a fair point that δεῖπνον does not always signify the evening meal, but it usually did. How do we know when δεῖπνον refers to an evening meal? A good indicator is context. For example, one might render the word as "banquet" in Rev. 19:9. See https://www.revisedenglishversion.com/Revelation/chapter19/9
On the other hand, it's a bit strong to say 1 Cor. 11:20, 25 NWT "is an overtranslation." The translation "evening meal" falls squarely within the semantic domain of δεῖπνον; besides, Thiselton also professes that δεῖπνον normally did happen in the evening. Yet there's other reasons that Bowman's statement is misguided. However, to answer his challenge in this blog post, the timing of the meal is dictated by context and there are good reasons for understanding δεῖπνον as an "evening meal" in 1 Cor. 11:20, 25.