To Replace Something
To Substitute Something, To Exchange Something
transitive verb, ichidan verb
You know the kanji is substitute, and you know this is a verb. There are other similar ones, but this one means to replace something. In order to remember that this particular word means "to replace something" focus in on the え. You have an egg in your hands that you notice isn't any good (it's black and moldy). So, you replace it with another egg (or substitute it with another egg, or exchange it with another egg, etc).
This verb is transitive, meaning it has a direct object. You replace something, like that egg!
The reading for this one is the same as 代わる which you learned in a previous level. As long as you know that one you should be able to learn this one's reading as well.
Should we replace this part with gold?
Please substitute cow's milk with almond milk.
The life of this puppy cannot be replaced with money.