Aperture Grill
A metal mask found inside a monitor that determines the spacing between the dots of light on a screen. Many less expensive monitors use an iron aperture grill, which tends to heat up and distort the image. A newer type of aperture grill, the Invar shadow mask, does not distort upon heating.

Cathode Ray Tube (CRT)
A glass tube which is the main component of a monitor. One end of the CRT serves as the monitor screen. At the back end of the CRT is an electron gun which fires a beam of electrons at the screen to display images.

Dot Pitch
The unit of measurement indicating how closely dots of the same color are spaced on the screen. A smaller dot pitch gives a sharper appearance, while a larger figure will result in a fairly fuzzy picture. Most monitors have a dot pitch of 0.28 millimeters.

Vertical Refresh Rate
The rate at which the full screen is redrawn, in cycles per second or hertz (Hz). When a monitor has a low refresh rate, the image appears to flicker. Anything over 72 Hz is considered fine, with 75 or 80 Hz considered quite good.