arctangent vs circular function

arctangent and circular function both are nouns.

Word	Noun	Adjective	Verb	Adverb
arctangent	Yes	No	No	No
circular function	Yes	No	No	No

As nouns, circular function is a hypernym of arctangent; that is, circular function is a word with a broader meaning than arctangent:

arctangent: the inverse function of the tangent; the angle that has a tangent equal to a given number
circular function: function of an angle expressed as a ratio of the length of the sides of right-angled triangle containing the angle

Other hypernyms of arctangent include trigonometric function.

arctangent (noun)	circular function (noun)
the inverse function of the tangent; the angle that has a tangent equal to a given number	function of an angle expressed as a ratio of the length of the sides of right-angled triangle containing the angle