# membranes

/ˈmɛmˌbɹeɪnz/ (US) · /mˈɛmbɹeɪnz/ (UK) · CEFR C1 · Noun

Source: https://englishreference.com/word/membranes
Updated: 2026-05-06

## Definition

thin layers of material that act like a skin, covering parts of a body or a cell. They let some things pass through while keeping others out.

For teachers: thin, pliable layers of tissue that line organs or connect structures within an organism; in biology, the semi-permeable lipid bilayer surrounding a cell.

## Examples

- The cell membrane protects the internal parts of the cell.
- Doctors found that the protective membranes around the patient's lungs were slightly inflamed, causing pain during deep breaths.
- Advanced filtration systems utilize synthetic membranes to desalinate seawater, mimicking the selective permeability found in biological systems to separate salt ions from water molecules.

## Usage notes

- Often appears in the plural when referring to biological structures or layers.

---

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.