The growth of ontologies in biomedicine.

<p>To illustrate the increasing use of ontologies, we mined PubMed abstracts for occurrences of the words <i>ontology</i> and <i>gene ontology</i> (and the plural forms thereof). We normalized for the general growth of PubMed by converting the raw counts per year to “hits per million abstracts.” The plot shows a steady increase in the awareness of ontologies over the past decade, and that GO became the dominating biological ontology over a period of just five years (note the logarithmic scale). However, ontologies appear to have reached a plateau over in the past three years, at least in terms of how often they are mentioned in abstracts. In contrast, the citations to GO and associated resources are steadily rising (end of 2009>5500) and imply a further increasing use.