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Onto- is a combining form used like a prefix meaning “being.” It is occasionally used in technical terms, especially in philosophy.

The form onto- comes from Greek ṓn, meaning “being.” The Latin equivalents are ŧ�Բ�, ent- and essent- “being,” which are the sources of entity and essence.

What are variants of onto-?

When combined with words or word elements that begin with a vowel, onto- becomes ont-, as in ontic. When used as a suffix at the end of a word, onto- becomes -ont, as in diplont. Want to know more? Read our 51�Թ�s That Use articles for ont- and -ont.

One example of a term from philosophy that features the form onto- is ontology, the branch of metaphysics that studies the nature of existence. Ontology comes from the New Latin ontologia, which uses the equivalent form of onto- in the language.

The onto- part of the word means “being,” but what about the -logy part of the word? It may look familiar from words like biology; the form -logy is used to name areas of study or branches of science, from Greek ���Dz�í��. Ontology literally means “the study of being.”

What are some words that use the combining form onto-?

• ontogenesis
• ontogenetic
• ontogeny
• ontological
• ontologize

What are some other forms that onto- may be commonly confused with?

• onco-
• oneiro-
• oto-

The combining form -geny means “origin.” With this in mind, what does the biological term ontogeny mean?