IPA: /ˌaɪsəʊˈθɜːməli/
KK: /ˌaɪsəʊˈθɜːrməli/
In a way that maintains a constant temperature during a process or reaction.
The gas expanded isothermally, keeping the temperature steady throughout the experiment.
Isothermally → It is formed from "iso-" (meaning equal) and "thermos" (from Greek θερμός, meaning heat) and the suffix "-ally" (meaning in a manner). The word "isothermally" refers to a process occurring at equal temperature throughout.
Think of 'equal' ('iso-') heat ('thermos') to remember that 'isothermally' means something happening at a constant temperature.