Risk and safety are polyvalent concepts with numerous and overlapping ethical complexities in relation to science and technology. As such they are dealt with in a number of different entries.

In technical terms, scientific phenomena may exhibit certainty, risk, or uncertainty. Situations of certainty have a probability of 1. For example, all things being equal, it is certain (probability = 1) that water freezes when cooled below 0° Celsius. Cases of risk have some numerical probability between 0 and 1, based on a known or assumed model of what causes the outcome under study. For instance, the risk of tossing "heads" on a fair coin has a probability of 0.5, because the model is known. In risk assessment, the risk of something is typically defined as the average annual estimated probability of causing a fatality. Cases of uncertainty cannot be defined a priori in terms of probabilities, because of...