"Idea" is typically considered a count noun. It can be used in both singular and plural forms and can be counted as individual units.
Examples of "idea" as a count noun:
I have a great idea for the project.
She shared several interesting ideas during the meeting.
The team came up with dozens of new ideas to improve sales.
While "idea" is generally considered a count noun, it can also be used in a non-count sense to refer to the concept or notion of having thoughts or creativity, rather than specific individual ideas.
Example of "idea" as a non-count noun:
The book explores the idea of freedom and self-expression.
She has a knack for coming up with creative ideas.
In this non-count noun usage, "idea" is not referring to specific, quantifiable concepts, but rather to a general concept or theme.