Are scientific laws, theories, and terms capitalized?

The MLA follows The Chicago Manual of Style in recommending that scientific laws, theories, and terms be lowercased except when preceded by a proper adjective (ch. 8, sec. 148). We also consult Merriam-Webster’s Collegiate Dictionary for spelling, which generally adheres to Chicago’s principle. The following provides examples:

Laws, Theories, and Terms with Proper Adjectives

Pythagorean theorem

Einstein’s general theory of relativity

Schr√∂dinger’s equation

Fermat’s last theorem

Bayesisan statistics

Cartesian coordinate

Newton’s first law of motion

Mendel’s law

Avogadro’s number

Heisenberg’s uncertainty principle

Euclidean algorithm1

Laws, Theories, and Terms without Proper Adjectives

general theory of relativity

big bang theory

string theory

field theory

quantum theory

law of definite proportions

conservation of mass

binomial theorem

uncertainty principle


See also our related post on citing mathematical theories.

1Merriam-Webster lowercases “euclidean” in “euclidean geometry” but also notes that the e in “euclidean” is “often capitalized” (“Euclidean Geometry”). Either form would be acceptable in MLA style.

Works Cited

The Chicago Manual of Style. U of Chicago P, 2021,

“Euclidean Geometry, N.”¬†Merriam-Webster, 2021,