Originally Answered: I am teaching nouns (person, place, thing, or idea). But how do I explain the definition of 'thing' and 'idea?
By definition, a "thing" is as follows:
a material object without life or consciousness; an inanimate object.
2. some entity, object, or creature that is not or cannot be specifically designated or precisely described: The stick had a brass thing on it.
3. anything that is or may become an object of thought: things of the spirit.
4. things, matters; affairs: Things are going well now.
5. a fact, circumstance, or state of affairs: It is a curious thing.
6. an action, deed, event, or performance: to do great things; His death was a horrible thing.
7. a particular, respect, or detail: perfect in all things.
8. aim; objective: The thing is to reach this line with the ball.
9. an article of clothing: I don't have a thing to wear.
a. implements, utensils, or other articles for service: I'll wash the breakfast things.
b. personal possessions or belongings: Pack your things and go!
11. a task; chore: I've got a lot of things to do today.
12. a living being or creature: His baby's a cute little thing.
13. a thought or statement: I have just one thing to say to you.
14. Informal. a peculiar attitude or feeling, either positive or negative, toward something; mental quirk: She has a thing about cats.
15. something signified or represented, as distinguished from a word, symbol, or idea representing it.
So you see - a "thing" can be alive or inanimate. It can also be an entity, so "math class" is a thing too.
An idea is defined as follows:
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.
a. a concept developed by the mind.
b. a conception of what is desirable or ought to be; ideal.
c. (initial capital letter) 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.
An idea is not tangible but more a concept. "Love" is an idea.