StockPile
A pile of face-down cards that players may draw from; located to the left of the Discard Pile.

Discard Pile
A pile of face-up cards that players may discard to and draw from; located to the right of the Stock Pile.

Hand

A personal collection of up to 11 cards that is composed of Melds and Deadwood.

Upcard
The card that is placed in the discard pile before the first turn begins.

Meld
A Set or Run of cards in a player's hand; also known as a "lay".

Set
A collection of 3 or 4 cards of the same rank; also known as a "group".

Run
A collection of 3 or more cards of the same suit in sequential rank; also known as a "sequence".

Deadwood
Cards in a player's hand which are not part of a Meld; when deadwood is 10 or less, a player may knock.

Points

The combined value of a player's Deadwood; see Rules for details.

Knock
Ending the round by discarding a face-down card after having 10 or less points of Deadwood.

Undercut
Having equal or less deadwood than a knocking opponent that didn't go Gin or Big Gin; worth 25 bonus points (or 10 bonus points, depending on your Settings).

Gin
A hand containing 10 melded cards; worth 25 bonus points which is applied during the scoring sequence.

Big Gin
A hand containing 11 melded cards; worth 31 bonus points which is applied during the scoring sequence.

Layoff
Giving an unmatched card to an opponent (only when it fits into one of their melds) after knocking.