back up

phrasal verb·4 senses·particle up

Meanings

1

Make a digital copy of data as a safeguard

Why “up”? Something is held up for a while. A host can support a guest, or you can carry a burden.

Back up your files before the update.
Make safety copies of your files before the update.
She backed up the photos to an external drive.
She made safety copies of the photos on an external drive.
2

Support someone's claim, story or position

Will you back me up at the meeting?
Will you publicly support me at the meeting?
A second team backed them up on the ground.
A second team supported them on the ground.
We need more nurses to back up the night shift.
We need more nurses to reinforce the night shift.
3

Move backward along the same path

Why “up”? Backing up means moving a short way back along the same path. You go against the forward direction.

Back up slowly, there is a wall behind you.
Move backward slowly because there is a wall behind you.
The driver backed up to let the bus pass.
The driver moved backward to make space for the bus.
4

(of traffic or water) accumulate because flow is blocked

Increaseuncommon

Why “up”? More of something is higher. Quantity, intensity and speed all rise.

Traffic backed up for miles after the crash.
Traffic built up for miles after the crash.
Water backed up in the kitchen sink.
Water built up in the kitchen sink because the drain was blocked.

Don't confuse with

back upback out

Back up means make a digital copy of data as a safeguard. Back out means withdraw from a commitment or agreement.

Test yourself

Back up your files before the update. What does it mean?

Nearby in the meaning map

Sink In connects verbs by particle pattern, contrast pairs, and shared base verbs.

Tell it apart

Side-by-side comparisons with the verbs learners most often confuse for “back up”.

Practice “back up” in Sink In

Drill this and 600+ phrasal verbs with spaced repetition, organised by particle.