In linear algebra, a vector is written in a number of different ways: as a variable with an arrow over top, as column vector, or as one of many other notations. Typically, a vector appears in text like this:
In plain language, this represents the vector that is of degree .
When writing a vector as a variable, often an arrow is drawn over top and the variable is displayed in a non-italics and bold font.
The advantage of using this notation is, when referring to the components that make up a vector, you can differentiate the components from the vector itself.
In this case, it’s clear that is the first component of the vector and is the vector itself.