plural of air level

A spirit level.

(of two contestants) equal (having the same number of points, or being in the same position)

plural of Abney level

A clinometer used to measure tree heights.

plural of level crossing

(military, US) A person who has qualified for "Craftsman" level of skill in the United States Air Force, with more training than "Journeyman" (five-level), but less than a "Superintendent" (nine-level)

The total chemical potential for electrons.

plural of Fermi level

A delicate level pivoted so as to tilt when two parts of a measuring apparatus come into contact with each other; used in precise determinations of lengths and in the accurate graduation of instruments.