singular vs remarkable

singular is a noun but remarkable is not a noun.

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

As adjectives, singular and remarkable are synonyms defined as:

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

singular (adjective)	remarkable (adjective)
grammatical number category referring to a single item or unit	unusual or striking
composed of one member, set, or kind	worthy of attention
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