Mommy, Bean and Goobs are at the table. Bean and Goobs are having their dinner.
Bean: "What are we doing tomorrow Mommy?"
Mommy: "Tomorrow is swimming.I think your regular teacher is out of town so you are going to have a substitute."
Bean: "What does substitute mean Mommy?"
Mommy: "A substitute is when you replace something with something else to do the same job. Like if I didn't have buttermilk for a recipe, I could substitute it with milk and a little lemon juice. Your teacher is going to be out, so they are substituting her with someone else."
Bean continues to eat his dinner. Mommy can see he is thinking.
Bean: (Looks at Mommy an smirks. He is dying to use his new word, but he wants to play a little game with Mommy.) "Mommy, if Daddy needed to fix the glass on his car and he didn't have more glass he could use plastic instead."
Mommy: (Pleased as punch that her little three year old just got the concept she was explaining. She knows he is playing a game with her) "So you could substitute it, huh."
Bean: (Coily looks at Mommy and nods his head as if he has just taught her something.) "Yes I could substitute it Mommy. Very good."