What is the difference between “likelihood” and “probability”?

Question

What is the difference between "likelihood" and "probability"?

Iv'e check the dictionaries for that questions and it seems that there's no a difference. Cambridge dictionary even call them clearly also synonyms. But Wikipedia makes me a little bit confused about it:

"Probability is the measure of the likelihood that an event will occur."

So if they're the same we can say that "the probability is the measure of the probability that an event will occur." and it from wikipedia definition it seems that they're two different things.

So are they really synonyms and interchangeable in all if not most of the cases or there are cases that I should use one of them only?

For example:

• There is an high probability/ likelihood that today will be rainy.
• The likelihood / probability that spermatozoön will go to the uterus tissue is very low.
• The probability / likelihood for such event is not really real.
• The probability / likelihood that we will have class on Saturday is 50 %.

In all of these cases, it is just a matter of choice which one (probability or likelihood) to chose?

Answer 1

As is often the case when there are two synonyms, one of Germanic origin (here, likelihood) and the other of Latinate origin (probability), the Latinate one is preferred for formal and scientific contexts and the Germanic one tends to be used in informal contexts. Many native speakers do not learn the Latinate words until they reach secondary school.

Both words involve a scale of some kind.

When speaking of the likelihood that something will happen, we don't expect precision. We would say that something has little likelihood of happening or great likelihood or not much likelihood or a decent likelihood of happening.

There's little likelihood that she will arrive at work by 8:30AM. The train she is taking is notorious for running late. There's always some "signal problem" or "personnel problem" or some other excuse for their mismanagement.

When speaking of the probability that something will happen, the context may often demand a number, and if the context doesn't ask for precision, we would say that the thing has either a low probability or a high probability of happening.

So, given these differences, probability can also refer to the act of measuring or calculating how likely or unlikely something is, assessing its likelihood.

Answer 2

There is no real difference, except that probability is used more often with a percentage as in your last example.

Either one works for the examples you gave interchangeably.