A dimension specifies a distance. Dimension are used to specify sizes of things, such as the length of a line. Dimensions are written using a factor (a multiplier) and a unit of measure.
Units of measure
The font-independent units of measure that TeX understands are:
- pt: point (72.27 points = 1 inch)
- pc: pica (1 pica = 12 points)
- bp: big point (72 big points = 1 inch)
- in: inch
- cm: centimeter (2.54 centimeters = 1 inch)
- mm: millimeter (10 millimeters = 1 centimeter)
- dd: didôt point (1157 didôt points = 1238 points)
- cc: cicero (1 cicero = 12 didôt points)
- sp: scaled point (65536 scaled points = 1 point)
The font-dependent units of measure are:
- ex: a vertical measure usually about the height of the letter 'x' in the current font
- em: a horizontal measure usually equal to the point size of the current font and about the width of the letter 'M' in the font
Finally, TeX provides three "infinite" units of measure: 'fil', 'fill' and 'filll', in increasing order of strength.
Usage
A dimension is written as a factor (a multiplier) followed by a unit of measure, for example:
1cm -3.5in 0em 2fill
The last of these represents an infinite distance. TeX only accepts infinite distances when specifying the stretch or shrink of a glue. An infinite distance outweighs any finite distance or any weaker infinite distance. For example, if you add 1000in or 2fil to -1fill, then you obtain -1fill.