The gradient (slope) of the line on the graph.
The slope of a distance-time graph represents speed.
9.95
speed
speed
You could try a speed-time graph, or a distance-time graph.
constant speed
The slope of a time vs distance graph represents the speed or velocity of an object. It is calculated as the change in distance divided by the change in time. A steeper slope indicates a greater speed.
The gradient (slope) of the tangent to the graph at the given time - provided that it exists. If the graph is a straight line at that point, it is the gradient of that line.
The steepness of the line on a distance-time graph represents the radial speed of the object. That is, the speed with which the object is moving towards or away from the origin. The steepness takes absolutely no account of the transverse speed, so you can be going around the origin in a circle at a great speed but, since your distance remains the same, the D-T graph will be flat: implying speed = 0.
deceleration or negative
The speed. Also, if a positive slope represents the speed in one direction, the negative slope is the speed in the opposite direction.
The variable plotted along the vertical axis is the distance in the first case, speed in the second. The gradient of (the tangent to) the distance-time graph is the speed while the area under the curve of the speed-time graph is the distance.