- -1: the product of the slopes of two perpendicular lines
- constant of variation: what the k is in the equation y = kx
- direct variation: y = kx
- horizontal line: appears in the form y = a where a is any number
- parallel lines: lines that have the same slope
- perpendicular lines: the slopes of these lines are negative reciprocals of each other (ie. m and -1/m)
- point-slope form: y - y₁ = m(x - x₁)
- rate of change: another name for slope, usually in reference to speed
- slope: (y₂ - y₁)/(x₂ - x₁)
- slope: rise over run (also known as m)
- slope-intercept form: y = mx + b
- standard form: Ax + By = C
- vertical line: appears in the form x = a where a is any number
- x-intercept: point where the line crosses the x-axis
- y-intercept: point where a line crosses the y-axis (also known as b)