Gambling terms, explained straight

Odds, Probability & Bankroll

Probability vs possibility

Probability measures how likely an event is to occur on a scale from 0 to 1, while possibility measures how feasible or plausible an event is, often using separate possibility and necessity measures.

Scale
Probability: 0 to 1 (0% to 100%). Possibility: possibility and necessity measures, also 0 to 1.12
Core idea
Probability handles "either-or randomness"; possibility handles "both-and fuzziness".3
Example
A coin has a 50% probability of landing heads. It is possible the coin lands on its edge, though the probability is near zero.
Use case
Probability is used in gambling odds and risk modelling; possibility is used in fuzzy logic and risk communication.4

Key points

  • Probability assigns a single numeric likelihood to an event, often from observed frequencies or degrees of belief.26
  • Possibility theory represents uncertainty with separate possibility and necessity measures, where possibility reflects the "ease" an event can occur.15
  • In gambling, probability drives odds calculation; possibility is rarely used but appears in alternative uncertainty models for risk communication.4

Probability vs possibility examples

A standard die has a probability of 1/6 (about 16.7%) of rolling a 3. It is possible to roll a 7 with a standard die? No — a standard die has no 7 face, so the possibility is zero. But it is possible to roll a 3, even though the probability is only 16.7%. This shows possibility is a binary or graded measure of feasibility, while probability quantifies likelihood.

In gambling, a horse might have a 10% probability of winning (implied by odds of 9/1). It is possible the horse wins, but the probability is low. Possibility theory would assign a high possibility (it is feasible) and a low necessity (it is not certain).

Where this term is used

Odds & probability Odds vs probability Explains the difference between odds (a ratio of outcomes) and probability (a likelihood measure). Odds & probability Likelihood vs probability Covers the distinction between likelihood (evidence for a hypothesis) and probability (expected frequency). Odds & probability Implied probability Shows how to convert betting odds into an implied percentage chance of an outcome. Odds & probability Probability of a straight Calculates the chance of being dealt a straight in poker using combinatorial probability. Odds & probability Straight flush probability Gives the exact probability of a straight flush in poker, including royal flush. Odds & probability Betting odds to probability A guide to converting fractional, decimal and American odds into probabilities.

Sources

  1. Possibility theory en.wikipedia.org Defines possibility theory and its measures of possibility and necessity.
  2. Probability en.wikipedia.org Defines probability as a number between 0 and 1.
  3. 1 arxiv.org Contrasts possibility as 'both-and fuzziness' with probability as 'either-or randomness'.
  4. Communicating Risk with Possibility, Not Probability arxiv.org Discusses using possibility instead of probability for risk communication.
  5. A Concept of Possibility for Real-World Events - arXiv arxiv.org Describes possibility as the 'ease' with which an event can occur.
  6. A brief introduction to probability - PMC - NIH pmc.ncbi.nlm.nih.gov Explains probability as a measure from observed frequencies or degrees of belief.

Sources are drawn from regulators, universities and published research, and each one is labelled with what it actually is — a preprint is not called a paper. Bookmaker and affiliate pages are never cited here, because a page that sells betting is not a neutral authority on it.

Written and maintained by Ellis Warrender, writer and maintainer.

Last updated 28 July 2026. Spotted an error? Tell me and it gets fixed and logged on the corrections page.