These include structural mechanics, studying how forces affect structures like bridges and buildings; fluid mechanics, essential for understanding water flow in hydraulic structures; geotechnical engineering, focusing on soil and rock behavior to support foundations; and transportation theory, examining traffic flow and infrastructure optimization. Additionally, materials science theories inform material selection and durability considerations. Environmental engineering theories address sustainability and pollution control. Each theory integrates with practical applications, ensuring safe, efficient, and sustainable infrastructure development. How do these theories collectively shape the modern practice of civil engineering, and what challenges do they address?