DEFINITION:

i·de·a
1.any conception existing in the mind as a result of mental understanding, awareness, or activity.
2.
a thought, conception, or notion: That is an excellent idea.
3.
an impression: He gave me a general idea of how he plans to run the department.
4.
an opinion, view, or belief: His ideas on raising children are certainly strange.
5.
a plan of action; an intention: the idea of becoming an engineer.
6.
a groundless supposition; fantasy.
7.
Philosophy .
a concept developed by the mind.
a conception of what is desirable or ought to be; ideal.
c. Platonism . Also called form. an archetype or pattern of which the individual objects in any natural class are imperfect copies and from which they derive their being.

i·de·al
–noun
1.
a conception of something in its perfection.
2.
a standard of perfection or excellence.
3.
a person or thing conceived as embodying such a conception or conforming to such a standard, and taken as a model for imitation: Thomas Jefferson was his ideal.
4.
an ultimate object or aim of endeavor, especially one of high or noble character: He refuses to compromise any of his ideals.
5.
something that exists only in the imagination: To achieve the ideal is almost hopeless.
6.
Mathematics . a subring of a ring, any element of which when multiplied by any element of the ring results in an element of the subring.
–adjective
7.
conceived as constituting a standard of perfection or excellence: ideal beauty.
8.
regarded as perfect of its kind: an ideal spot for a home.