Term: layer
https://doi.org/10.1351/goldbook.L03488

Definition:
Any conceptual region of space restricted in one dimension, within or at the surface of a condensed phase or a film. The usage of the term 'film' for an adsorption layer is confusing and is discouraged. The term double-layer applies to layers approximated by two 'distinct' sublayers.

Related Terms:
1) film (http://doi.org/10.1351/goldbook.F02366).

Source: PAC, 1994, 66, 1667. 'Thin films including layers: terminology in relation to their preparation and characterization (IUPAC Recommendations 1994)' on page 1671 (https://doi.org/10.1351/pac199466081667)

Citation: 'layer' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.L03488

License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms.

Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.