Definition:Percentage

Definition
A percentage is a convenient way of expressing (usually) a fraction as an easily-grasped number, by multiplying it by $100$ and appending the symbol $\%$ which means per cent.

As conventionally understood, the number being rendered as a percentage is between $0$ and $1$, thus determining the range of a percentage to be $0 \%$ to $100 \%$.

However in many contexts that range is frequently extended (in particular, in the field of rhetoric):
 * I want every member of this team to give one hundred and ten percent.

Also denoted as
The common phrase per cent can often be seen rendered as percent.

Some older works, from an era when punctuation was required to be more precise, render the phrase as per cent., that is, with a following "." in order to indicate that it is an abbreviation.

It is a welcome evolution of the English language that such fussiness has since been dispensed with.