What is Down ?
Down is (prep) 1. towards the bottom of He fell down the stairs and broke his leg. The ball ran down the hill. 2. away from where the person speaking is standing He went down the road to the shop. The police station is just down the street. (adv) 1. towards the bottom, towards a lower position Put the box down in the corner. I looked in the cellar, but there’s no one down there. (NOTE: Down is often used with verbs, e.g. to go down; to fall down, to sit down; to lie down.) 2. at a lower level Inflation is down again. 3. in writing Did you note down the number of the car? The policeman took down her address. 4. towards the south I’m going down to Brighton tomorrow (from London). They live down on the south coast. 5. sick She is down with flu. 6. out of action All our computers are down at the moment. 7. gloomy He’s feeling a bit down. 8. showing criticism Down with the government! Down with exams! (noun) the soft small feathers of a bird a duvet filled with duck down (NOTE: no plural in this meaning) (verb) 1. to swallow something quickly He downed three pints of beer. 2. to down tools to stop work, to go on strike
source: Easier English, Student Dictionary Upper Intermediate Level