In its simplest form, you can define it simply using a pair of coordinates. You can either express these as an ordered pair, or with the x- and y-coordinates specified in their own attributes:
You can add droplines (vertical and/or horizontal) by saying what their labels should be. If you just want droplines with no labels, include the attribute but leave it blank.
You often want to label a point. Since the label uses the coordinates of the point, you just need to specify the text and the position of the label. The default, as in point A below, is to display the label above and to the right of the point. If you want to change this, use the position attribute. We follow the LaTeX convention of thinking of the position from the label’s point of view, not the point: so specifying tr, as in point B below, means the top-right corner of the label is touching the point – that is, the label appears below and to the left of the point.
Points are blue by default; use the color attribute to change the color. Droplines and labels inherit the color of the point.
Both labels and dropline labels are rendered as LaTeX. If you need to label them using text (or mixed math and text), use the \text{} command for the text strings.