A textual resource, comprising one or more dictionaries, is termed a lexical resource. Within this, a lexical database is a resource equipped with an associated software environment database, enabling access to its contents. Databases are generally classified as custom-designed or general-purpose. They typically feature comprehensive semantic, syntactic, and phonetic details about words and multiword expressions. Additionally, lexical data encompasses semantic and phonological relationships between words, along with translation equivalents across various languages. Natural language processing applications, dictionary creators, and users rely on lexical data for various purposes. This book is a compilation of chapters that discuss the most vital concepts and theories in the field of language modeling. The topics covered herein deal with the core subject of lexical resource. This book is an essential guide for both academicians and those who wish to pursue this discipline further.