Captioning: The process of converting narration, dialogue, music and sound effects of a video production into text that is displayed on a television screen. The captions are typically white upper-case letters against a black background.

Prerecorded (Off-line) Captioning: The preparation of captions for recorded programming so that, at the time of air or tape playback, the captions are a part of the videotape. Appearance of captions is usually "pop-on" but could also be "roll-up." Captions are typically placed in the upper or lower third of the television screen.

Pop-on Captions: A phrase or sentence appears on the screen all at once – not line by line – stays there for a few seconds and then disappears or is replaced by another full caption. The captions are timed to synchronize with the program and placed on the screen to help identify the speaker. Pop-on captions are used for prerecorded captioning.

Roll-up Captions: Roll-up captions roll onto and off the screen in a continuous motion. Usually two to three lines of text appear at one time. As a new line comes along, it appears on the bottom, pushing the other lines on the screen up. Roll-up captions are used for all live captioning and can also be used for prerecorded captioning.

Timed Roll-Up Captions: For prerecorded programming, roll-up captions can be timed to be closely synchronized with the audio.

Live (On-line) Captioning: Captioning that is provided at the time of program origination. "Real-time," "live-display" and a combination of the two are all methods of on-line captioning. Appearance of captions is "roll-up."

Real-time Captioning: Method of captioning in which captions are simultaneously prepared and transmitted at the time of origination by specially trained real-time captioners using a stenotype machine.

Closed Captions: Captions that can only appear with the use of a decoder. The decoder may be either attached to a TV or built into TV's made after July 1993. Closed captioning allows caption users to enjoy the same broadcast and recorded video materials that other television viewers enjoy. Closed-caption information is carried in Line 21 of the vertical blanking interval of the television signal.

Open Captions: Captions that are visible without using a set-top decoder or a TV with a built-in decoder chip. When a video is open captioned, the captions are permanently part of the picture.

Closed Caption Decoder: A small electronic device that decodes the captioning signal and causes captions to appear on the screen. In the 1980's and early 1990's, closed caption decoders were the major means by which consumers could watch captioned television. Since July 1, 1993, all television sets with screens 13 inches or larger manufactured for sale in the United States must have a built-in decoder chip.

Caption File: A computer file that stores a program's caption information, including the text, timing and placement information. The caption file is used in conjunction with an encoder to create the captioned submaster.

Encoding: The process of inserting the caption data into the television signal on Line 21.

Encoder: A device that electronically inserts the caption data into the TV signal on Line 21

Line 21: The television signal is comprised of 525 lines. The vertical blanking interval encompasses Line 1 through 21. The caption information resides on Line 21, and active video starts on Line 22.

Time-code: An electronic signal embedded in a videotape that discretely identifies each frame of video.

Master: The original, first-generation videotape of the final version of a program. The master is the source videotape used to create a captioned "submaster."

Submaster: Any duplication created from the master videotape. The captioned videotape is a submaster of the original.

Subtitles: Permanent on-screen text that represents the narration and dialogue of a program. Subtitles are created with a character generator; no decoding capability is required for viewing them. Subtitles are usually in upper- and lower-case letters and do not appear in a black background. Also, subtitles are typically placed at the bottom center of the screen.

Reformat: The process of revising previously captioned programs for rebroadcast, requiring the retiming and/or editing of caption text to synchronize it to the edited video and audio.