Flush draw
A flush draw is four cards of one suit with more cards still to come, so one more card of that suit completes a flush.
The arithmetic is fixed. Thirteen cards share a suit, four of them are already visible to you, so nine are left among the 47 cards you have not seen after the flop.
That is 19.1% on the turn alone and 35.0% by the river if you see both cards. The second figure only applies if you actually get to the river, which is why a flush draw is worth more in position than out of it.
an example
your cards
board
Two hearts in your hand and two on the board leave nine hearts in the deck. If the pot is 100 and you are asked to call 50, you need 25% and you have 35.0% with two cards to come, so the price is good.
This example is made up. The real one is in your own hand history: find flush draw in your own hands and see how often it came up and what it cost you.
related terms
Outs
An out is a card still in the deck that would give you the best hand, and counting them is how you turn a draw into a nu ...
Draw
A draw is a hand that is not worth much yet but becomes strong if one of a known set of cards arrives.
Flush
A flush is five cards of the same suit, which beats a straight and loses to a full house.
next
Knowing the word is not the same as seeing it.
Forty hands against a bot, no account, and your own hand history at the end.