adjective
fortuitous
for-TOO-ih-tus/fɔːrˈtuːɪtəs/
Happening by chance rather than by design.
Her discovery of the banknote while tying her shoe is fortuitous.

Etymology
Latin fortuitus describes something happening by chance rather than design. Chance is the inherited idea; the lucky implication in the selected sense adds a favorable outcome.
In context
And it was fortuitous that the Wellcome Trust were having one of their regular meetings on the Wednesday of the following week when we were looking at budgets.
More examples
- Their discovery was fortuitous rather than planned.
- The timing is a fortuitous coincidence.
- A fortuitous change in the weather saves the outdoor event.
Forms
fortuitous
Similar words
- accidental
- Can suggest an unintended mishap rather than a lucky coincidence.
- coincidental
- Coincidental stresses chance conjunction; fortuitous more broadly means unplanned and often fortunate.