# incompatible

/ˌɪnkəmˈpætəbəɫ/ (US) · /ɪnkəmpˈætəbəl/ (UK)

Source: https://englishreference.com/word/incompatible
Updated: 2026-08-08

## Senses

### 1. unable to coexist

adjective · CEFR B2

describes two things that are so different they cannot exist or work together at the same time.

For teachers: describes two or more things that are incapable of existing together in harmony or working in conjunction due to fundamental differences.

- Their personalities were incompatible, so they decided to stop working together.
- The new software update proved incompatible with the older operating system, causing the entire network to crash during the migration.

Usage: often used with the preposition 'with'

### 2. chemical/medical reaction

adjective · CEFR C1 · Technical

describes chemicals or medicines that cause a bad reaction if you mix them.

For teachers: incapable of being combined without undergoing a chemical change or producing an undesirable medical effect.

- The two cleaning liquids are incompatible and could create dangerous fumes if mixed.
- The pharmacist warned that the two medications were chemically incompatible and must be administered at least four hours apart.

Usage: typically used in medical or laboratory contexts

Teaching tip: This is a specialized use; in everyday English, 'incompatible' usually refers to people or technology.

### 3. conflicting things

noun · CEFR C2 · Formal · Technical

a person or thing that cannot be combined with another.

For teachers: 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.

- The lab report listed several incompatibles that should never be stored in the same cabinet.
- In the study of logic, the two propositions were treated as incompatibles, as the truth of one necessitated the falsehood of the other.

Usage: most commonly found in medical or scientific literature in the plural form

Teaching tip: The noun form is quite rare compared to the adjective; students should focus on the adjective first.

## Examples

- The new software is incompatible with my old computer.
- The two political parties found their core values were incompatible, making a coalition government impossible.
- In chemistry, mixing incompatible substances can lead to dangerous reactions, while in logic, two incompatible statements cannot simultaneously be accepted as true within the same framework.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.