Final answer:
The prefix 'circum' means 'around' or 'on all sides', used to describe something encircling another.
Step-by-step explanation:
The word 'circum' is a prefix that means 'around' or 'on all sides'.
It is used to form words that describe something that is surrounding or encircling another object.
For example, the word 'circumference' uses this prefix to indicate the distance around a circle.