The dominant language in server-side web development is JavaScript, particularly with the introduction of environments like Node.js. This enables developers to build scalable and efficient web applications using JavaScript for server-side logic. Other prominent languages include PHP, which powers many content management systems, and Python, known for its simplicity and versatility. Each of these languages plays a crucial role in managing server operations, handling databases, and creating dynamic content that interacts with users. The choice often depends on project requirements, performance considerations, and developer proficiency.