back up

back up — phrasal verb

  • back upbase form
  • backs up3rd person singular
  • backing up-ing form
  • backed uppast simple

1. to give help or encouragement to a person, group, or plan, especially when the s

1.片語動詞及物B1
釋義

to give help or encouragement to a person, group, or plan, especially when the situation is difficult — for example, backing a colleague's proposal in a meeting or supporting a friend who is being criticised.

例句

When the policy was attacked, the CEO backed her team up before the board.

back + someone + up in a formal setting

Théo's parents backed him up when he decided to leave his job and open a bakery.

backed + person + up when [decision]

同義詞
  • support

    more general; 'back up' often suggests support in a public or defensive situation

  • stand by

    similar but emphasises loyalty rather than active help

  • defend

    stronger, implies the person/idea is under attack

反義詞
  • oppose

    to be against someone or something

  • undermine

    to weaken someone's position instead of supporting it

文法句型

back someone/something up

back up someone/something

用法筆記

Common in workplace and community contexts. The object can come before or after 'up': 'backed her team up' or 'backed up her team'.

常見錯誤

❌I backed up to him during the argument.
✅I backed him up during the argument.
💡'back up' in this sense needs a direct object; it cannot be followed by 'to'.

2. to confirm the truth of someone's statement, especially by offering your own kno

2.片語動詞及物B1
釋義

to confirm the truth of someone's statement, especially by offering your own knowledge or experience — for instance, telling a supervisor that a coworker's version of events matches what you saw.

例句

Ravindra told police he saw the car at midnight, and his neighbour backed him up.

backed + [person] + up = confirm their account

The hospital records backed up the nurse's report about the patient's condition.

inanimate subject: records backed up [statement]

同義詞
  • corroborate

    more formal, typically used for evidence or official statements

  • verify

    focuses on checking facts rather than supporting a person

  • confirm

    more general; 'back up' implies you are helping someone else's version

反義詞
  • contradict

    to say the opposite of what someone has stated

  • dispute

    to argue that a claim is not true

文法句型

back someone up

back up someone's statement

用法筆記

Frequently used with an inanimate subject (documents, records, evidence) to mean 'corroborate'. Distinguish from sense 1 (SUPPORT): here the focus is on confirming the truth of a statement, not giving general help.

常見錯誤

❌She backed up to him about what happened.
✅She backed him up about what happened.
💡'back up' in this sense is transitive; the person whose statement is being confirmed is the direct object.

3. to provide facts, evidence, or good reasons that show an idea, theory, or claim

3.片語動詞及物B2
釋義

to provide facts, evidence, or good reasons that show an idea, theory, or claim is correct — for example, showing sales figures to prove your argument that a product is selling well.

例句

The scientist backed up her theory with data collected over three years of field research.

back up + [claim] + with + [evidence]

Hugo's teacher asked him to back up his answer with examples from the book.

back up + [answer] + with + [examples]

同義詞
  • substantiate

    more formal; mainly used in academic or legal writing

  • support

    general; 'back up' implies concrete evidence specifically

  • validate

    focuses on checking that something meets a standard

反義詞
  • disprove

    to show that a claim is false

  • refute

    to prove a statement is wrong with evidence

文法句型

back something up with something

back up a claim

用法筆記

This sense is close to sense 2 but broader: you back up a CLAIM or ARGUMENT rather than a person. Often appears in academic, legal, and professional contexts. The preposition 'with' is very common: 'back up [something] with [evidence]'.

常見錯誤

❌He backed up his idea of examples.
✅He backed up his idea with examples.
💡use 'with', not 'of', to introduce the supporting evidence.

4. to make a copy of digital information, such as documents, photos, or system data

4.片語動詞及物A2
釋義

to make a copy of digital information, such as documents, photos, or system data, so that the original can be restored if it is lost, damaged, or accidentally deleted.

例句

Tamás backs up his photos to an external hard drive every Friday evening.

back up + [data] + to + [location]

The company server backs up all customer records automatically every night.

automatic backup: server backs up + [data]

同義詞
  • save

    more general; 'back up' specifically means creating a copy for safety

  • copy

    simpler but less specific; a copy is not necessarily a backup

反義詞
  • delete

    to remove data permanently

文法句型

back up a file

back up data

back something up to [location]

用法筆記

This sense is the most common modern use of 'back up'. Frequently used without an object in instructions: 'Remember to back up regularly.' The noun form 'backup' (one word) refers to the copy itself.

常見錯誤

❌I backed up my computer to the cloud.' (ambiguous — could mean moving backwards)
✅I backed up the files on my computer to the cloud.
💡name the specific data being copied to avoid confusion with the 'drive backwards' sense.

5. to move a car, truck, or other vehicle in a reverse direction — for example, dri

5.片語動詞及物 / 不及物A2
釋義

to move a car, truck, or other vehicle in a reverse direction — for example, driving out of a parking space or reversing down a driveway.

例句

Felipe backed up slowly out of the narrow driveway, checking both mirrors.

back up + out of + [location]

The delivery truck backed up to the loading dock so the workers could unload it.

back up + to + [destination]

同義詞
  • reverse

    more formal or technical; 'back up' is more common in everyday speech

反義詞

文法句型

back up (intransitive)

back a vehicle up

back up out of [place]

用法筆記

Can be used transitively (back a vehicle up) or intransitively (just back up). When transitive, the object is always a vehicle. The intransitive form is more common in everyday conversation.

常見錯誤

❌I backed up the car backwards.
✅I backed up the car.
💡'back up' already means 'move backwards' so 'backwards' is redundant.

6. when vehicles on a road become so numerous that they cannot move freely and form

6.片語動詞不及物B1
釋義

when vehicles on a road become so numerous that they cannot move freely and form a long, slow-moving line — for example, after an accident on the highway or during rush hour.

例句

Traffic backed up for three kilometres after a lorry broke down on the motorway.

traffic backed up for + [distance]

During the festival, cars backed up from the town centre to the bridge.

cars backed up from [X] to [Y]

同義詞
  • queue up

    used for people or vehicles; 'back up' is specifically for vehicular traffic

  • pile up

    suggests multiple vehicles in a chain; more informal

反義詞

文法句型

traffic backs up

cars back up

traffic backed up for miles

用法筆記

Only used with traffic or vehicles as the subject. Not used for people queuing. The noun form 'backup' (one word) is also common: 'There was a huge backup on the highway.'

常見錯誤

❌The people at the bus stop backed up.
✅The traffic backed up at the intersection.
💡'back up' for congestion is only used for vehicles, not people.