A sparer is someone who is careful with their money. They are usually more frugal than spenders, and they are more likely to save their money.
To betray someone is to betray their trust. You might betray someone by telling them something that you shouldn't have, or by not being loyal to them.
Deviating means to go out of the normal way that something is done. When you deviate from the standard recipe, you might end up with a recipe that is not very good.
Smug is a word that people often use to describe people who are feeling too good about themselves. They are usually very confident and think that they are better than everyone else.
To betray someone is to break their trust. When you betray someone, you break the trust that they have in you.
To retaliate is to take action in response to somebody else's action. When the student retaliated against the teacher, they retaliated against her with bad grades.
sentient is a word that is used to describe something that is able to think and feel. Everything that exists is either sentient or not, but some things are more sentient than others.
To erode is to wear away or destroy something. The soil can erode away the foundation of a building, and the erosion of the ocean can destroy the coastlines.
demonstrably means that there is no doubt about it. It is clear and obvious, and there is no need for further discussion.