The process of attaching additional information to biological entities. Annotation can be structural (i.e. identification of the elements from a sequence, such as protein coding regions or the location of regulatory motifs) or functional (i.e. adding biological information to the identified elements, such as the biological function of a protein domain or an entire protein, or the molecular interactions or regulatory role of a nucleotide sequence). Annotation can either be applied automatically or can be manually added (in a process called 'curation') from various sources, such as the scientific literature. At EMBL-EBI, we use a combination of automatic and manual annotation to enrich our databases.