A data warehouse in the context of big data is a centralized repository that stores large volumes of structured and unstructured data from various sources. It is designed to facilitate data analysis and reporting, enabling organizations to derive insights and make informed decisions. Unlike traditional databases, a data warehouse uses ETL (Extract, Transform, Load) processes to integrate and consolidate data from disparate sources, ensuring compatibility and quality. This allows businesses to perform complex queries and analysis more efficiently, making it a key component of data-driven strategies and business intelligence.