An isolating (or 'analytic') language is defined as one in which all words are invariable. Isolating language is a traditional term used for languages in which there is very little (overt) morphology. Separate grammatical concepts or functions tend to be conveyed by separate words and not by morphological processes. Chinese and Vietnamese are isolating languages.
Chinese is often cited as a well-known example of the isolating type of language.
Lyons, John. 1968. Introduction to Theoretical Linguistics. Cambridge: Cambridge University Press.