Substitution failure is not an error
So imagine you have a puzzle and you need to put the pieces in the right places to make a picture. But sometimes, you might have a piece that looks like it should fit in a certain spot, but when you try to put it there, it just doesn't work. That's kind of like what substitution failure is.
Substitution failure happens when you try to put one thing in place of another thing, but it doesn't work like you thought it would. And that's okay! It's not a mistake or an error, it just means that particular thing doesn't fit in that particular place.
For example, let's say you have a recipe that calls for butter, but you don't have any butter, so you decide to use margarine instead because they look similar. But then when you try to use the margarine, it doesn't work as well as the butter would have. The recipe might not turn out exactly the same, but that doesn't mean you did something wrong. It's just a substitution failure.
Substitution failure happens when you try to put one thing in place of another thing, but it doesn't work like you thought it would. And that's okay! It's not a mistake or an error, it just means that particular thing doesn't fit in that particular place.
For example, let's say you have a recipe that calls for butter, but you don't have any butter, so you decide to use margarine instead because they look similar. But then when you try to use the margarine, it doesn't work as well as the butter would have. The recipe might not turn out exactly the same, but that doesn't mean you did something wrong. It's just a substitution failure.