incompatible
- 01 B2 Upper Intermediate
adj.describes two things that are so different they cannot exist or work together at the same time.
adj.describes two or more things that are incapable of existing together in harmony or working in conjunction due to fundamental differences.
Simple“Their personalities were incompatible, so they decided to stop working together.”
In context“The new software update proved incompatible with the older operating system, causing the entire network to crash during the migration.”
Usageoften used with the preposition 'with'
SynonymsAntonyms - 02 C1 Advanced
adj.describes chemicals or medicines that cause a bad reaction if you mix them.
adj.incapable of being combined without undergoing a chemical change or producing an undesirable medical effect.
Simple“The two cleaning liquids are incompatible and could create dangerous fumes if mixed.”
In context“The pharmacist warned that the two medications were chemically incompatible and must be administered at least four hours apart.”
Usagetypically used in medical or laboratory contexts
Teacher's tipThis is a specialized use; in everyday English, 'incompatible' usually refers to people or technology.
SynonymsunmixableAntonyms - 03 C2 Proficiency
n.a person or thing that cannot be combined with another.
n.a person or thing that is fundamentally different from or unable to coexist with another; often used in the plural to describe substances that react poorly together.
Simple“The lab report listed several incompatibles that should never be stored in the same cabinet.”
In context“In the study of logic, the two propositions were treated as incompatibles, as the truth of one necessitated the falsehood of the other.”
Usagemost commonly found in medical or scientific literature in the plural form
Teacher's tipThe noun form is quite rare compared to the adjective; students should focus on the adjective first.
Synonyms
“Spain missed the official January 10th 2026 EU transposition deadline, creating legal friction with Brussels over aligning domestic banking rules which the EU says are incompatible with the new regulations.”
“Even professional monitoring programs still struggle with limited staff, outdated software or incompatible standards, further slowing the flow of data.”
Borrowed from French incompatible.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.