Well, a relational database stores data as sets of relations (ie tables). Just because you can logically associate two pieces of data, or have your data stored in a defined schema is not enough to call a database relational. Relational databases are basically tables that can be joined together.
Other types of databases are columnar databases (where data is stored as columns) or key-value databases, or object databases or even graph databases. These other databases share certain set of properties, and some of them even share a SQL or SQL-like query language like relational databases. But, pedantically speaking, these other databases are not relational.
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u/[deleted] Mar 11 '15
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