This document describes a study of the lexicons used in the REST APIs of three cloud computing providers: Google Cloud Platform (GCP), OpenStack, and the Open Cloud Computing Interface (OCCI). The study found strong diversity between providers in terms of the number of services and URIs offered. Each provider's lexicon was unique, with no terms common across all three APIs and only 17 terms shared between two APIs. The study aims to provide the first analysis of lexical heterogeneity across cloud computing REST APIs and identify opportunities to improve semantic interoperability.