arctan vs circular function

arctan and circular function both are nouns.

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

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

arctan: 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 arctan include trigonometric function.

arctan (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