What does a slope of zero indicate about a line?

A slope of zero indicates that there is no change in the y-coordinate as the x-coordinate changes. This means the line does not rise or fall; instead, it remains constant at a particular y-value across all x-values. As such, the line is perfectly horizontal.

In mathematical terms, slope is defined as the "rise" over "run," which corresponds to the change in y divided by the change in x. If the slope is zero, the numerator (change in y) is zero while the denominator (change in x) is not, resulting in a fraction that equals zero. This characteristic clearly defines a horizontal line, where y stays the same regardless of x. Understanding this concept is fundamental in graphing linear equations and interpreting their meaning in various contexts.