This is the 345th most frequent Catalan word.
idea
A thought, concept, or plan formed in the mind.
The word 'idea' here is used to denote a personal thought or a concept formulated to resolve or contribute to something (noun usage).
Tinc una idea per al projecte.
I have an idea for the project.
In this sentence, 'idea' refers to a specific good concept or thought previously conceived by someone (compliment and reference to creativity).
Quina bona idea vas tenir ahir!
What a great idea you had yesterday!
The word 'idea' highlights a notion or plan characterized as being creative or unique (adjectival description).