fill up — to make something completely full
phrasal verbB1IELTS 5+neutralcommon
To put something into a container or space until there is no more room left.
Say it like a native
Textbook I need to completely replenish the fuel tank.
Native I need to fill up the tank.
'Fill up' is the natural verb for filling something completely; 'completely replenish' is over-formal.
Pattern: fill up (something) / fill (something) up
In use
- I need to fill up the car with petrol before our trip.daily life
- Whenever I go on a long drive, I always fill up the tank to avoid running out of fuel.IELTS speaking
Common mistake
✗ I filled up it with petrol.
✓ I filled it up with petrol.
With a pronoun, the object goes in the middle: 'fill it up'.
Common collocations
fill up + container— the tank, the car, with water, on snacks
Don't confuse it
'Fill' can mean to put something in, but 'fill up' stresses that it is full to the top.