# ESA

CEFR C2 · Noun

Source: https://englishreference.com/word/esa
Updated: 2026-05-07

## Definition

a test used by scientists to measure the amount or activity of a specific substance in a sample. It is common in medicine and biology to check for things like drugs or proteins.

For teachers: an investigative procedure in medicine, pharmacology, or biology for qualitatively assessing or quantitatively measuring the presence, amount, or functional activity of a target entity.

## Pitfalls

- Not "the assay for check the blood" but "the assay to check the blood" — When used as a noun, it is typically followed by an infinitive or 'for' plus a noun phrase, not 'for' plus a base verb.

## Usage notes

- Often used in technical or scientific contexts; can function as both a noun and a transitive verb.

---

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.