they're both general terms, but serve different purposes. Data Warehouses tend to focus on read-specific operations, more of an emphasis on historical and/or analytical problems than transactional ones. Subsequently they are likely to optimize data ingress, distributed queries and downplay referential integrity and consistency. The different workloads promote different compute models, but you're right that the line is blurry. Similarly you could ask "Excel has multiple tables (sheets) that you can join and query; is it a database"?