# PIA

/ˈpiə/ (US) · CEFR C2 · Noun

Source: https://englishreference.com/word/pia
Updated: 2026-05-10

## Definition

Stands for pia mater. The thin, delicate layer that covers the brain and spinal cord. It is the innermost of the three layers that protect your central nervous system.

For teachers: Abbreviation for pia mater. The delicate, vascularized innermost layer of the meninges that directly envelopes the brain and spinal cord. It follows the contours of the brain's surface, dipping into the sulci and fissures.

## Examples

- The pia is the layer closest to the brain.
- During the surgery, the doctor carefully avoided damaging the pia to protect the underlying neural tissue.
- The meninges consist of three distinct membranes—the dura mater, the arachnoid mater, and the pia mater—which collectively serve to protect the central nervous system from mechanical injury.

## Usage notes

- Often referred to by its full Latin name, 'pia mater'.

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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.