L Terms
Ligature You know this is when two letters are combined to form one, like in Þ or þ. But did you know that all type that is connected, such as most scripts, is said to be ligated?
Lining Figures are numbers that all have the same optical baseline-that's the opposite of oldstyle figures.
M Terms
Metrics All of the information about how a font fits together, like kerning information and character widths.
MicroType A font-compression/format technology from Monotype Imaging that is used to make fonts very, very small in equipment that ships with built-in fonts, like laser printers. It's part of Monotype Imaging's Universal Font Scaling Technology which is used by many printer manufacturers for handling internal font generation. If you're Hewlett-Packard and you ship millions of printers a year, every little bit of information represents a manufacturing cost, so the smaller the font, the less memory you have to build in to the printer. MicroType Express is a version of the technology for electronic document distribution that has caught the eye of Microsoft, among others, who have licensed it for possible use in future products. Everyone wants to have the type-compression technology of the future (see TrueDoc, Intellifont).
Modifier Key Since keyboards aren't big enough to dedicate a single key to every letter, symbol or number, modifier keys exist to access single characters by deploying two (or more) keys in sequence or in tandem. The shift key is the most basic modifier key. On the Mac, the most common modifier key is the option key or the control key. On a PC keyboard, the option key is generally called the alternate key or escape key. Sometimes called the effector key, and if you have any old typesetters around the office, you may still hear them refer to the option key as the bell key.
Mouse You think it's just that pointing device next to your keyboard. Well, it's also the rubber-cement pickup device from old paste-up days.
Multiple Masters Developed by Adobe, these fonts consist of at least two (and up to 16) master outlines that can be combined to form an almost endless variety of weights, widths and heights of a particular design. They are a good bet if you work quite a bit with the same type style. Gives you lots of flexibility in copyfitting and design.