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Published September 12, 2026 · By Vincent KENNEL
Risk, issue, uncertainty, contingency: four words we confuse
Risk, issue, uncertainty, contingency: four words that turn up in the same sentence and carry four different commitments. What each one answers, where they come from, and why a single French word keeps blurring the line.
In brief
A risk has not occurred; an issue has. Uncertainty is the state of not knowing. Those three answer what we know. Aléa and contingency answer a different question: who carries the event, and with what. Five words, two questions, and no synonyms among them. Two traditions claim aléa, and that is where the confusion begins.
On a programme under contract, the same event is often recorded three times over. It is a risk in the risk review, an issue in the monthly report, and contingency in the cost report. The three entries travel in three different documents, and nobody notices that they do not commit the same person to the same thing.
Five words, two questions
Uncertainty, risk, issue, aléa and contingency are not five names for one thing. They answer two different questions, and working out which one a word belongs to is most of the job.
What we know: uncertainty, risk, issue
Uncertainty is a state. ISO 31073:2022 defines it as a "state, even partial, of deficiency of information related to understanding or knowledge", and adds that uncertainty "is the root source of risk". It says nothing about an event: it describes what is known. That wording is recent. In the earlier edition, ISO Guide 73:2009, uncertainty was not a term at all, only a note attached to the entry for risk and tied to an event.
A risk is an event that has been identified and has not occurred. The PMBOK Guide 6th Edition calls it "an uncertain event or condition that, if it occurs, has a positive or negative effect on one or more project objectives", and PRINCE2 7 "an uncertain event or set of events that, should it occur, will have an effect on the achievement of objectives". ISO 31073:2022 comes at it from the other end, as the "effect of uncertainty on objectives", and the PMBOK Guide holds both together by separating individual project risk, which is the event, from overall project risk, which is the effect on the project as a whole. In every one of them the effect runs both ways. ISO 21502:2020 says so in its own terms: an opportunity is a "risk occurrence that would have a favourable impact", a threat one "that would have a negative impact".
An issue is an event that has occurred. ISO 21502:2020 describes issue resolution as "recording and handling an event or problem that has happened and threatens the success of the project or represents an opportunity to be exploited", and it separates the two in its structure as well: clause 7.8, Risk management, and clause 7.9, Issues management, are distinct and consecutive. The PMBOK Guide 6th Edition draws the same line, defining an issue as "a current condition or situation that may have an impact on the project objectives".
Those three words all answer one question: what is known, and when. The two that follow answer another one entirely, which is who carries the event and with what. And that junction is where French lays a trap, because one word is claimed from both sides.
Who carries it, and with what: aléa, contingency
Aléa is a French word with no single English counterpart, and two traditions define it differently.
In French contract law it points to what remains on one party's account. In its decision of 30 March 1916, no. 59928, the Conseil d'État held that a variation in raw material prices was an aléa of the contract, favourable or unfavourable depending on the case, and one that remained at the concessionaire's own risk. Article 1108 of the French Code civil, as amended by ordonnance no. 2016-131 of 10 February 2016, rests on the same idea when it calls a contract aléatoire where the parties agree to make its effects depend on an uncertain event. This is description, not legal advice.
In project management the same word is defined by something else, unpredictability. The Dictionnaire de management de projet (AFITEP, 3rd edition, 1996) describes aléas as events that could not be foreseen at the time of the initial estimate, and the Office québécois de la langue française gives aléas as a synonym of imprévus, both rendered in English as contingencies.
Two traditions therefore place the same word on two different axes. This article does not arbitrate between them, and notes only what follows: a word claimed from both sides travels easily and explains very little.
Contingency, in the cost engineering sense, is what an estimate sets aside for what it knows it will spend without being able to book it line by line. AACE International Recommended Practice No. 10S-90 (Rev. 11 June 2026) defines it as "an amount added to an estimate to allow for items, conditions, or events for which the state, occurrence, or effect is uncertain and that experience shows will likely result, in aggregate, in additional costs", and adds the part that surprises people: contingency "is generally included in most estimates and is expected to be expended". It is not a pot to be defended.
What each word commits, on a project under contract
Calling an event an aléa says, without anyone deciding it, that the price already covers it. Calling it a risk says that it is still open and still to be treated. Calling it contingency says that money has been set aside against it. Three statements about who absorbs the cost, carried by a choice of word rather than by a decision.
Where it matters, the contractual reading is explicit. The EIA-748-D Intent Guide (Revision D, 2018) states at Guideline 14 that management reserve "is not a contingency that can be eliminated from prices during subsequent negotiations or used to absorb the cost of project changes", and that the budget held in reserve "must not be viewed by a customer as a source for added work scope". Article 1195 of the French Code civil, as amended by ordonnance no. 2016-131 of 10 February 2016, reserves the right to renegotiate, on an unforeseeable change of circumstances, to the party that had not accepted to bear that risk. Acceptance is the legal criterion, and it is the management criterion too. Again, description rather than advice.
How much each envelope holds, who releases it and how it is sized are separate questions, and they belong to the article on contingency reserve and management reserve.
Where these words come from
The pair that causes most of the trouble, risk and uncertainty, was first treated rigorously more than a century ago, and by an economist rather than by a project body. Frank H. Knight published Risk, Uncertainty and Profit in 1921. Chapter VII carries the title "The Meaning of Risk and Uncertainty", and page 233 states the criterion:
"The practical difference between the two categories, risk and uncertainty, is that in the former the distribution of the outcome in a group of instances is known (either through calculation a priori or from statistics of past experience), while in the case of uncertainty this is not true, the reason being in general that it is impossible to form a group of instances, because the situation dealt with is in a high degree unique."
For Knight the dividing line is measurement, and measurement rests on one condition: whether a class of comparable occurrences can be formed. Where it can, the outcome has a distribution. Where it cannot, because the situation is in his words in a high degree unique, there is no distribution to estimate.
That condition describes a great deal of what happens on a large programme under contract. A first-of-class integration, or a decision awaited from a single regulator, is not a repeated event with a history behind it. The vocabulary of project management borrowed both words long afterwards, and borrowed them already carrying that distinction.
The safe reflex is to state which glossary is in use before employing contingency or reserve. The PMBOK Guide 6th Edition and GAO-20-195G (March 2020) both use contingency and management reserve, and they do not attach the two words to the same thing. AACE 10S-90 turns that into a rule rather than a complaint: uncertainty is "a term that may have various meanings for which the convention used in any specific application should be clearly stated to avoid misunderstanding".
Two reflexes
Two things follow, and both apply to the next document that crosses a desk.
The first is to place the word on its axis before using it. Does it answer what is known, or who carries the cost? A word that cannot be placed is read one way by whoever writes it and another way by whoever signs it.
The second is to write every risk as a cause, an event and a consequence. Four independent references converge on that form. The Orange Book (HM Treasury, May 2023) states that risk "is usually expressed in terms of causes, potential events, and their consequences"; PRINCE2 7 asks its risk description field for "a summary of the cause, event, and effect of the risk"; ECSS-M-ST-80C (2008) defines a risk scenario as a "sequence or combination of events leading from the initial cause to the unwanted consequence"; and ISO 31073:2022 says the same in a note to its own definition. The vocabulary is unstable; the form is not. What a risk register should hold beyond that description is the subject of a separate article.
Stop guessing. See the real impact.
Frequently asked questions
Q.Does a risk always mean something bad?
No. ISO 31073:2022, the PMBOK Guide 6th Edition and PRINCE2 7 all describe the effect of a risk as favourable or unfavourable. ISO 21502:2020 names both cases: an opportunity is a risk occurrence with a favourable impact.
Q.Is there an English word for aléa?
Not one that carries both senses. In project management the word points to what could not be foreseen when the estimate was made. In French contract law it points to what stays on one party's account. English splits the two.
Q.How is the size of a contingency decided?
Not in this article. It settles what the word means, not how much money it stands for. Sizing is a matter of estimating method, and the envelope itself, who holds it and who releases it, belongs to a separate article.
References
AACE International - AACE International Recommended Practice No. 10S-90 - Cost Engineering Terminology - Rev. 11 June 2026
AFNOR, AFITEP - Dictionnaire de management de projet français-anglais-espagnol - 3e édition, 1996
