(set theory) One of the axioms in axiomatic set theory that guarantees the existence of an infinite set.

(set theory) One of the axioms in axiomatic set theory, equivalent to the statement that a union exists for any set, containing exactly all the elements contained within the sets within that set.

(set theory) One of the axioms in axiomatic set theory, equivalent to the statement that every non-empty set contains a member that is disjoint from that set.

(geometry) Either of two axes in a conic section, such that each is parallel to the tangent at the extremity of the other.

simple past tense and past participle of axenize

(medicine) A xanthine oxidase inhibitor that reduces uric acid concentration in the blood

(herpetology) Coloured without normal yellow or red pigments, resulting in shades of grey.

Skill in using an axe (tool for chopping wood).

(mechanical engineering) Of a traction motor, mounted on the axle it drives.

(geometry) A statement in plane geometry, used implicitly by Euclid, which cannot be derived from Euclid's postulates. It states that, if a line, not passing through any vertex of a triangle, meets one side of the triangle then it meets another side.