From Longman Dictionary of Contemporary Englishldoce_339_etraytray /treɪ/ ●●○ S3 noun [countable] 1 
Da flat piece of plastic, metal, or wood, with raised edges, used for carrying things such as plates, food etc The waiter brought drinks on a tray.2 Ba flat open container with three sides used for holding papers, documents etc on a deskin tray (=for holding documents you still have to deal with)out tray (=for holding documents you have dealt with)3 especially British English a flat open container with four sides used for holding certain things a cat litter trayseed tray (=a tray in which you plant seeds) → baking tray, system tray
Da flat piece of plastic, metal, or wood, with raised edges, used for carrying things such as plates, food etc The waiter brought drinks on a tray.2 Ba flat open container with three sides used for holding papers, documents etc on a deskin tray (=for holding documents you still have to deal with)out tray (=for holding documents you have dealt with)3 especially British English a flat open container with four sides used for holding certain things a cat litter trayseed tray (=a tray in which you plant seeds) → baking tray, system trayExamples from the Corpus
tray• The door opened and Jenkins entered carrying a tray.• We had tomato soup for dinner, followed by roast beef and sago pudding, served airline-style on a tray.• She heard Stephen order Sally to take a tray upstairs to Mrs Winters and she said nothing.• Water Grill's dessert tray beckons!• If bulbs look shrivelled when unpacked, immerse in trays of damp peat until plumped out.• There are many more, including wheelchairs, sticks, commodes, special non-slip trays, and bath seats.• The tray was heavy with food and drinks.seed tray• Because polyanthus are more difficult to germinate, start them off in seed trays or pots in a greenhouse or cold frame.• Use a small split cane the width of the seed tray to make a series of depressions in the levelled compost.Origin tray Old English trig, treg 