idea vs generalisation

idea and generalisation both are nouns.

Word	Noun	Adjective	Verb	Adverb
idea	Yes	No	No	No
generalisation	Yes	No	No	No

As nouns, generalisation is a hyponym of idea; that is, generalisation is a word with a more specific, narrower meaning than idea:

idea (noun)	generalisation (noun)
the content of cognition; the main thing you are thinking about	an idea or conclusion having general application
your intention; what you intend to do	reasoning from detailed facts to general principles
an approximate calculation of quantity or degree or worth	(psychology) transfer of a response learned to one stimulus to a similar stimulus
a personal view	the process of formulating general concepts by abstracting common properties of instances
(music) melodic subject of a musical composition