Some nouns that are ideas (abstract nouns) that start with G are:
i have no idea but i think it starts with a g!
Georgia, Greg, Garth, Germany
germ
silliness, sound, skepticism, soulfulness, softness, surrender, simplicity, etc.
"pyramid" is a 7 letter common singular noun that clearly begins with "p" a noun is a person, place, thing, or idea- a "pyramid" is a thing
An idea that is a noun: idea
An "island" is a common noun that starts with the letter "i."
garden soil starts with G
Guyana starts with a "G"
Wikipédia is a French noun that starts with w.
Hopeful is an adjective, not a noun. The noun form, hopefulness is an abstract noun (if that's what an 'idea noun' means).
It Is Like this. Noun A 2 Words Describing Noun A 3 words that end with -ing That Describes Noun A 2 about Noun A And 2 From Noun G 3 words that end with -ing that describe Noun G 2 Words Describing Noun G Noun G. Just Like that!