What is the definition of word annum?

The word "annum" is a Latin word meaning "year". It's often used in phrases like:

* Per annum (p.a.) - meaning "per year"

* Annual - meaning "yearly"

It's typically used in financial or legal contexts to denote a period of one year. For example:

* "The interest rate is 5% per annum."

* "The company's annual revenue is $10 million."

While "annum" is often used in English, it's not as common as its synonym "year."