Project Details Recommendations for terms relating to materials characterization: Latin and other introduced terms

Project No.:
Start Date:
26 May 2021
End Date:


This project has the objective to clarify, as well as resolve discrepancies and conflict, regarding Latin terms used to describe the characterization of materials made under non-ambient conditions, materials within systems, and of materials during change. These include terms such as ex situ, in situ, and (in) operando. The outcome of the project will be a recommendation for specific Latin terms to the IUPAC. This objective will benefit the materials chemistry community and empower IUPAC to make a decision on recommended terms for these. It is intended that the terminology will comply with the VIM and IUPAC Guidelines for Recommendations.


A variety of Latin-based terms for the characterization of materials under ambient conditions (such as ex situ), made under non-ambient conditions (such as in situ), materials within systems (such as in situ), and of materials during change (such as in operando or operando), have arisen in the community, for which no formal definitions exist. In particular, intense debate surrounding the use of the preposition for operando characterization has arisen, highlighting a need for formal definitions.

This project seeks to clarify definition of terms within the community and make a recommendation to IUPAC for a formal definition of terms. The project members include specialist researchers within the materials characterization community involved in this debate, Latin experts in conversation with these researchers, a co-Editor of the International Union of Crystallography’s Journal of Applied Crystallography, a journal publishing materials methods and characterization approaches, and IUPAC members involved in chemistry terminology. This group will have discussions, reach a consensus for correct terms and their definitions, and provide a recommendation to IUPAC for these.


Project announcement published in Chem Int Oct 2021, p. 32

January 2022 update – A terms list describing sample measurement conditions has been clarified and Latin/other existing definitions are being added. A recommendation for terms will follow.

Page last updated 13 Jan 2022