Definition Of Line. Keeping this fact in mind, by definition, the slope is the measure of the steepness of a line. Line definition, a mark or stroke long in proportion to its breadth, made with a pen, pencil, tool, etc., on a surface: a line down the middle of the page. It is called a line because, when plotted on a graph, it looks like a roughly horizontal line. Home Contact About Subject Index. Horizontal Line Test A test for whether a relation is one-to-one. Definition of 'horizontal' and comparison to its cousin 'vertical' Math Open Reference. A horizontal line is one which runs left-to-right across the page. Example of Line. Line definition is - a length of cord or cord-like material: such as. How to use line in a sentence. Horizontal Line Test Horizontal line test is used to determine whether a function has an inverse using the graph of the function. There are four types of slope you can encounter. If every horizontal line cuts the graph in at most one point, then the function has an inverse otherwise it does not. The representation for the line PQ is . Equation of a Line The standard form of line equation is Ax + By = C where A, B and C are real numbers, A 0 and x, y are variables.This standard form of line equation is used in algebra.The standard form of line equation can also be written as Ax + By - C = 0. The first step in creating a line plot is to give the line plot a title that will provide an overview of the data being displayed. In geometry, a horizontal line is one which runs from left to right across the page. Line 1. Horizontal. So, and represent lines. 2. See more. More About Line. Video Examples: Example of Tangent Line A Line is a straight path that is endless in both directions. In the above figure, NO and PQ extend endlessly in both directions. In real life, we see slope in any direction. I repeat we always measure slope going from left to right. However, in math, slope is defined as you move from left to right. In this lesson, you will learn the definition and properties of a straight line. In technical analysis, a situation in which the supply and demand for a security are largely the same. A line does not have any thickness. The title of this graph is 'Favorite Sport.' This is very important! A line means that the security is unlikely to see any rapid fluctuation in price.