Expert (noun) — a person who has a high level of special knowledge or skill in a particular field, gained through extensive training or experience. Expert (adjective) — done with, or requiring, great skill: expert advice; expert knowledge.
What Does Expert Mean?
Expert comes from the Latin expertus, the past participle of experiri, meaning "to try" or "to test through experience". It entered English via Old French in the late 14th century, originally carrying the sense of "tried and tested". This etymology is shared with experience, experiment, and even peril — all words rooted in the idea of testing something against reality. From the outset, the word implied not just knowledge but knowledge earned through direct engagement.
In modern British English, expert functions as both a noun and an adjective. As a noun it refers to a person whose mastery of a subject is recognised by others: a medical expert, a leading expert on climate change. As an adjective it describes a quality of performance or knowledge: expert craftsmanship, an expert opinion. The derived noun expertise (/ˌek.spɜːˈtiːz/) refers to the body of special knowledge or skill itself.
Note the stress pattern: the noun and adjective are both stressed on the first syllable — EX-pert. This contrasts with many two-syllable words in English that shift stress between noun and verb uses (e.g., RE-cord vs re-CORD). Expert does not follow that pattern; the stress never moves.
Example Sentences (A2 – C1)
| Sentence | Level & usage note |
|---|---|
| She is an expert in applied linguistics. | A2 — basic noun + prepositional phrase |
| We asked an expert to check the computer problem. | B1 — expert as object noun in everyday context |
| The government consulted several industry experts before changing the law. | B1 — plural noun in formal/civic context |
| Her expert knowledge of tax law helped the company avoid a costly mistake. | B2 — expert as attributive adjective modifying a noun phrase |
| The report was compiled with expert precision, drawing on a decade of longitudinal research. | C1 — expert modifying an abstract noun in academic register |
Common Collocations
| Collocation | Example |
|---|---|
| leading expert | She is a leading expert on renewable energy policy. |
| expert advice | Always seek expert advice before signing a contract. |
| expert opinion | The judge relied on expert opinion from a forensic scientist. |
| subject-matter expert | We need a subject-matter expert to review the technical manual. |
| expert witness | The defence called an expert witness to challenge the DNA evidence. |
| expert knowledge | His expert knowledge of medieval history impressed the panel. |
| consult an expert | If you are unsure, it is always best to consult an expert. |
| resident expert | She is the team's resident expert on data privacy regulations. |
| self-proclaimed expert | Be cautious of self-proclaimed experts who lack verifiable credentials. |
| expert panel | An expert panel reviewed all submissions before announcing the results. |
Usage Notes
Key Points for ESL Learners
Noun patterns: Use an expert in [field] or an expert on [topic]. Both prepositions are correct, but in tends to be used for broader disciplines (an expert in linguistics), while on is more common with specific topics (an expert on Brexit).
Adjective use: When expert is an adjective it always comes before a noun (expert advice, expert hands) or after a linking verb with a prepositional complement (She is expert at negotiation). The latter construction is more formal.
Expertise vs expert: Use expertise when you mean the body of knowledge itself: "Her expertise in phonology is widely cited." Use expert when referring to the person: "She is the expert we need."
Register: Expert is neutral to formal. In informal speech, people may instead say pro, whizz, or ace. In academic and professional writing, expert is the standard choice.
Common Mistakes
Watch Out For
She is an expert of climate change.
She is an expert on / in climate change. (use on or in, not of)
He expertised in machine learning for ten years.
He specialised in machine learning for ten years. (expert is not a verb)
According to expertises, the project is feasible.
According to experts, the project is feasible. (expertise is uncountable; for the person, use expert)