Even money means the profit equals the stake. It is written as 1/1 in fractional odds, 2.00 in decimal and +100 in American odds. The implied probability is 50%. Many casino bets are called even money, such as red or black in roulette, but they do not have a true 50% chance because of the zero. A bet that pays even money but wins less than half the time still has a house edge.
Example
A 10 unit bet on red in European roulette pays 10 in profit if red lands. The chance of red is 18 in 37, or 48.65%, not 50%.