The notation of a line over a variable, such as
is known as a "bar" or "vinculum".
Attached is the converted worksheet to P9. You can use it to make your own variable with "vinculum" following these steps:
1. Place the cursor to the right of T:
2. Type in your own letter (the "vinculum" will move to the right letter):
3. Place the cursor to the left of the new letter and hit backspace to delete the first letter:
In mathematics and other disciplines, this type of notation can serve various purposes. For example:
In statistics, it often represents the mean or average value of a set of numbers. So 
In physics, it can represent a time-averaged value over a cycle or period.
In number theory, it can represent the conjugate of a complex number.
In genetics, it can denote the wild type or normal allele of a gene.
In logic, it is used as a negation symbol.
The specific context in which the notation is used determines its meaning.
