phonogram vs written symbol

phonogram and written symbol both are nouns.

Word	Noun	Adjective	Verb	Adverb
phonogram	Yes	No	No	No
written symbol	Yes	No	No	No

As nouns, written symbol is a hypernym of phonogram; that is, written symbol is a word with a broader meaning than phonogram:

phonogram: any written symbol standing for a sound or syllable or morpheme or word
written symbol: a written or printed symbol

Other hypernyms of phonogram include printed symbol.

phonogram (noun)	written symbol (noun)
any written symbol standing for a sound or syllable or morpheme or word	a written or printed symbol