The chapter begins with the concept of language simplification, its definition and purposes. Next, it provides examples of English-based controlled languages for specialist communication and simplified Englishes for general purposes. The sections that follow introduce the concept of plain language and provide an overview of Plain English, its history, guidelines and vital role in effective communication in various fields. Subsequent sections present the concept, characteristics and classification of English for Specific Purposes, with a special emphasis on English for Research Publication Purposes, an offshoot of English for Academic Purposes. The remaining sections of this chapter provide insights into English as a prevalent language of scientific publication worldwide, the importance of language accuracy and the role of rhetorical conventions in scientific manuscripts intended for publication.