A format is metadata that descripes the data type, and character set of a data element.
DAMA NL (2020). Data concepts for Data Quality Dimensions (DSC). Research paper. https://www.dama-nl.org/wp-content/uploads/2020/09/DCS-Data-Concept-System-DDQ-Research-Paper-version-1.2-d.d.-3-Sept-2020.pdf