arc cosine vs circular function

arc cosine and circular function both are nouns.

Word	Noun	Adjective	Verb	Adverb
arc cosine	Yes	No	No	No
circular function	Yes	No	No	No

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

arc cosine: the inverse function of the cosine; the angle that has a cosine 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 arc cosine include trigonometric function.

arc cosine (noun)	circular function (noun)
the inverse function of the cosine; the angle that has a cosine 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