Draw, meld sets and runs, discard. The family the rest grew out of.
The root of a very large family. Draw a card, try to arrange your hand into sets and runs, discard a card. Everything else in the family is a variation on this.
A 52-card deck. Ten cards each for two players, seven for three or four, six for five or six. One card is turned face up to start the discard pile and the rest is the stock.
A set: three or four cards of the same rank. A run: three or more consecutive cards of the same suit.
Aces are low, so ace-two-three is a run and queen-king-ace is not, unless you agree otherwise.
Draw the top card of the stock or the top of the discard pile. Optionally lay down any melds face up in front of you, and optionally add cards to melds anyone has already laid down. Discard one card.
The first player to meld or lay off their entire hand and discard their last card goes out and ends the hand.
If you lay down your entire hand in one turn, having melded nothing beforehand, the score against everyone else is doubled.
The winner scores the value of the cards left in the other players' hands: court cards 10, aces 1, and number cards their face value.
Game is 100 points, or an agreed number.
Everything that follows — gin, 500, canasta, contract rummy — changes one part of this and keeps the rest.