# Sera

/ˈsɪɹə/ (US) · /sˈiəɹɐ/ (UK) · CEFR C2 · Noun

Source: https://englishreference.com/word/sera
Updated: 2026-08-15

## Definition

the plural form of serum. It refers to the clear, liquid part of blood that remains after it has clotted, often used in medicine or science.

For teachers: the plural of serum; refers to the clear, yellowish fluid that separates from blood during clotting. Often used in medical and biological contexts to describe fluids containing antibodies.

## Examples

- The lab tested several sera for signs of the virus.
- Researchers compared the immune responses across different animal sera to identify which species produced the strongest antibodies.
- The study required the collection of various sera from patients who had recovered from the infection to determine if their blood contained neutralizing proteins.

## Pitfalls

- Not "The sera is being tested." but "The sera are being tested." — Sera is the plural form of serum and requires a plural verb.

## Usage notes

- The plural form of 'serum'; takes a plural verb. While 'serums' is also acceptable in modern English, 'sera' remains the standard in scientific and academic writing.

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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.