Definition of up adverb from the Oxford Advanced Learner's Dictionary

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up

adverb
ʌp
 
; ʌp
 
 
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For the special uses of up in phrasal verbs, look at the entries for the verbs. For example break up is in the phrasal verb section at break.
1 towards or in a higher positionHe jumped up from his chair.The sun was already up (= had risen) when they set off.They live up in the mountains.It didn't take long to put the tent up.I pinned the notice up on the wall.Lay the cards face up (= facing upwards) on the table.You look nice with your hair up (= arranged on top of or at the back of your head).Up you come!(= said when lifting a child)2 to or at a higher levelShe turned the volume up.Prices are still going up (= rising).United were 3–1 up at half-time.The wind is getting up (= blowing more strongly).Sales are well up on last year.3 to the place where somebody/something isA car drove up and he got in.She went straight up to the door and knocked loudly.4 to or at an important place, especially a large cityWe're going up to New York for the day. (British English, formal) His son's up at Oxford (= Oxford University).5 to a place in the north of a countryThey've moved up north.We drove up to Inverness to see my father.6 into pieces or partsShe tore the paper up.They've had the road up (= with the surface broken or removed) to lay some pipes.How shall we divide up the work?7 completelyWe ate all the food up.The stream has dried up.8 so as to be formed or brought togetherThe government agreed to set up a committee of inquiry.She gathered up her belongings.9 so as to be finished or closedI have some paperwork to finish up.Do your coat up; it's cold.10 (of a period of time) finished; overTime's up. Stop writing and hand in your papers.11 out of bedI stayed up late (= did not go to bed until late) last night. (British English) He's up and about again after his illness.12 (informal) used to say that something is happening, especially something unusual or unpleasantI could tell something was up by the looks on their faces.What's up?(= What is the matter?)What's up with him? He looks furious.Is anything up? You can tell me.
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In North American EnglishWhat's up? can just mean ‘What's new?’ or ‘What's happening?’ There may not be anything wrong.
Idioms

be up to somebody

to be somebody's duty or responsibility; to be for somebody to decide
It's not up to you to tell me how to do my job.Shall we eat out or stay in? It's up to you.

not be up to much

(British English) to be of poor quality; to not be very goodHis work isn't up to much.

up against something

(informal) facing problems or oppositionTeachers are up against some major problems these days.She's really up against it(= in a difficult situation).

up and down

1 moving upwards and downwardsThe boat bobbed up and down on the water.2 in one direction and then in the opposite directionShe was pacing up and down in front of her desk.3 sometimes good and sometimes badMy relationship with him was up and down.4 (North American English, informal) if you swear up and down that something is true, you say that it is definitely true

up and running

(of a system, for example a computer system) working; being usedBy that time the new system should be up and running.

up before somebody/something

appearing in front of somebody in authority for a judgement to be made about something that you have done
He came up before the local magistrate for speeding.

up for something

1 on offer for somethingThe house is up for sale.2 being considered for something, especially as a candidateTwo candidates are up for election.3 (informal) willing to take part in a particular activityWe're going clubbing tonight. Are you up for it?

up there

(informal) among or almost the best, worst, most important, etcIt may not have been the worst week of my life but it's up there.OK, it's not my absolute dream, but it's up there.These people can't live without the Internet—it's up there with air and water.

up to something

1 as far as a particular number, level, etcI can take up to four people (= but no more than four) in my car.The temperature went up to 35°C.2 (also up until something) not further or later than something; until somethingRead up to page 100.Up to now he's been very quiet.3 as high or as good as somethingHer latest book isn't up to her usual standard.4 (also up to doing something) physically or mentally capable of somethingHe's not up to the job.I don't feel up to going to work today.5 (informal) doing something, especially something badWhat's she up to?What've you been up to?I'm sure he's up to no good(= doing something bad).
Usage noteUsage note: increaseDescribing an increaseStudent numbers in English language schools in this country increased from 66000 in 2008 to just over 84000 in 2009.The number of students increased by almost 30% compared with the previous year.Student numbers shot up/increased dramatically in 2009.The proportion of Spanish students rose sharply from 5% in 2008 to 14% in 2009.There was a significant rise in student numbers in 2009.The 2009 figure was 84000, an increase of 28% on the previous year.The 2009 figure was 84000, 28 per cent up on the previous year.As the chart shows, this can partly be explained by a dramatic increase in students from Spain. Language Banks at expect, fall, illustrate, proportion