Conversely, if odds are very small (1/1000), probability will also be very small, close to 0. As an example, if we have a probability of 0.8, that makes the odds 8/2, which we can reduce to 4/1, which equals 4.0. When probability rises from 0.5 to 1.0, odds rise from 1 to a number approaching infinity. This makes the odds of it happening 1.0 (50÷50). Think of flipping a coin it will come up heads 50% of the time, making the probability of it happening 0.5 (50% of 1). If the probability is exactly 0.5, then the odds are 1.0. If the probability is between 0 and 0.5, the odds will be below 1.0. Probabilities of 0 are the same as odds of 0.
Odds on the other hand are expressed as the likelihood of an event occurring divided by the likelihood of it not occurring. A probability is always expressed as a number between 0 and 1. There's a simple difference between probabilities and odds: the probability of an event occurring is a fraction of how many times you would expect to see that event occurring on a set number of occasions.
The majority of scientists generally refer to probabilities, not odds, but that is more a matter of tradition, there is no logical basis for it. In the majority of circumstances, neither is preferable to the other. Any chance can be numerically described as either odds or probabilities.
