This document presents CHESA (Compact Hierarchical Explicit Semantic Representation), a novel approach for representing word semantics in a compact hierarchical structure based on a predefined ontology (Wikipedia categories and articles). CHESA constructs semantic representations using a greedy algorithm that selects concepts based on a conditional overrepresentation criterion to balance coverage and size. Empirical evaluations show CHESA achieves state-of-the-art performance in measuring word semantic relatedness, outperforming other methods when representation resources are limited by generalizing semantics at varying levels of abstraction in its hierarchical structure.