singular vs curious

singular is a noun but curious is not a noun.

Word	Noun	Adjective	Verb	Adverb
singular	Yes	Yes	No	No
curious	No	Yes	No	No

As adjectives, singular and curious are synonyms defined as:

Other synonyms of singular include funny, odd, peculiar, queer, rum, rummy.

singular (noun)	curious (noun)
the form of a word that is used to denote a singleton

singular (adjective)	curious (adjective)
grammatical number category referring to a single item or unit	eager to investigate and learn or learn more (sometimes about others' concerns)
composed of one member, set, or kind	beyond or deviating from the usual or expected
unusual or striking
being a single and separate person or thing
the single one of its kind
beyond or deviating from the usual or expected