What does coincident mean?
The adjective 'coincident' describes things that occur at the same time or occupy the same place or position. Its most familiar use is temporal: two events that happen together are said to be coincident, as when a policy change was coincident with an economic downturn. The word also has a precise geometric and cartographic sense, describing lines, points, or boundaries that lie exactly on top of one another — a stricter notion than mere similarity. A third sense conveys agreement or correspondence, as when one account is coincident with another. 'Coincident' is formal to technical in register, appearing more often in scientific writing, legal texts, and careful prose than in casual conversation. It frequently takes the preposition 'with', as in 'coincident with the merger'. Distinguished from its cousin 'coincidental', which stresses chance rather than actual simultaneity, 'coincident' asserts genuine temporal or spatial overlap, making it valuable wherever precision about timing and position matters.
adjectiveOccurring at the same time, or occupying the same place or position. Also used to describe things that are in exact agreement or correspondence with one another.
- Occupying the same time; occurring simultaneously.
- Occupying the same space or position; exactly matching or corresponding (as in geometry or mapping).
- In agreement or consistent with something else.
"The two meetings were coincident, so she could attend only one of them."
"The rise of streaming services was roughly coincident with the decline of video rental stores."
"In the diagram, the two lines are coincident, meaning they lie exactly on top of each other."
While most people use 'coincident' to mean simultaneous, in geometry it means something far more precise — two figures that occupy exactly the same space, like two circles drawn perfectly on top of each other.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of coincident
The English adjective 'coincident' derives from the Latin verb 'coincidere', formed from the prefix 'co-' ('together') and 'cadere' ('to fall'), thus literally meaning 'to fall together'. The word entered English in the early modern period, likely in the late 16th or early 17th century, drawing on the same Latin root that gave rise to 'incident' and related terms such as 'occident' and 'accident'. It shares this origin with the noun 'coincidence' and the verb 'coincide', both of which developed from the same Latin source.
Related word forms
How coincident is actually used
Formal to technical in register; rare in everyday casual speech. In mathematics and physics, 'coincident' carries a precise spatial meaning (occupying identical position), which differs subtly from the looser temporal sense common elsewhere. Often used predicatively with 'with' (e.g., 'coincident with the reform').
Easily confused with coincident
Coincident describes things that actually occur together or occupy the same space or time, while coincidental describes something that happens by mere chance without apparent causal connection.
Coincidence is a noun referring to a chance occurrence of two similar things at the same time, whereas coincident is an adjective describing the actual temporal or spatial overlap.