luncheon
Word family
Synonym discussion
Sense: noun/1
All four words describe a meal-based social event, but they differ in register, time of day, and formality. 'Lunch' is the ordinary, everyday term for the midday meal — used at school, at work, and at home with no implication of ceremony. 'Luncheon' upgrades the register: it signals a planned occasion with invited guests, often with speeches, an honoured guest, or a charitable purpose, and is the standard form on printed invitations and conference programmes. 'Brunch' is a different time slot — late morning, blending breakfast and lunch — and is usually informal. 'Banquet' is also formal but larger in scale and typically held in the evening, with a multi-course meal. So choose 'luncheon' when the meal is midday AND planned AND formal; 'lunch' when any of those three is missing.
Common collocations
Etymology
'Luncheon' first appears in 16th-century English meaning a thick piece or hunk of food, possibly linked to the older word 'nuncheon' (a light midday snack of bread and drink). By the late 17th century it had narrowed to mean a light meal taken between breakfast and the main midday or evening meal, and from the 19th century onward it picked up the modern flavour of a formal midday gathering. The shorter, everyday 'lunch' is a back-formation from 'luncheon', not the other way around — the longer word came first.