The term for the detailed planning phase in software development is software design. This phase involves outlining architecture, components, interfaces, and data structures needed to meet system requirements. It serves as a blueprint guiding developers on how to translate specific functional requirements into a cohesive application. Effective software design addresses potential challenges, enhances maintainability, and improves user experience. It encompasses both high-level architectural design and detailed design specifications, ensuring that the final product aligns with initial goals.