Arabic Ontology is a linguistic ontology for the Arabic language, which can be used as an Arabic Wordnet with ontologically-clean content. People use it also as a tree (i.e. classification) of the concepts/meanings of the Arabic terms. It is a formal representation of the concepts that the Arabic terms convey, and its content is ontologically well-founded, and benchmarked to scientific advances and rigorous knowledge sources rather than to speakers’ naïve beliefs as wordnets typically do . The Ontology tree can be explored online.