Who, that, which?

Piggybacking off of my article on June 3rd, "Which "to" is it?" I have decided to keep these grammar lessons going. In writing, it is crucial to have correct word placement. There are many commonly misused words people use everyday not realizing what they are actually saying. A few of my favorites are below:

Accept vs. Except
Accept - a verb meaning to receive (ex: Dorothy will accept her award at the banquet this Friday evening.)
Except - a preposition or verb usually meaning excluding something (ex: I will take the house salad with everything except onions.")

Affect vs. Effect
Affect - a verb meaning to influence (ex: Tom had no idea losing his cellphone would have such an affect on him.)
Effect - a noun meaning result or a verb meaning to bring about (ex: My doctor said the worst side effect of this new medication is dry mouth.)

Principle vs. Principal
Principle - a noun meaning a basic truth or law (ex: The principle truth in the matter is the car still ran the red light and caused the accident.)
Principal - a noun meaning the head of a school or an organization, or a sum of money (ex: Our principal, Mr. Felber, was very involved in the neighborhood watch program. OR The principal on his bond is at least a quarter of a million dollars.)

Than vs. Then
Than - a conjunction used in comparisons (ex: Mark is taller than Brad.)
Then - an adverb denoting time (ex: The email is to be sent on Tuesday, then the fax on Friday.)

Who vs Which vs. That
Who - refers to a person (ex: Mary was looking for someone who would take her to the airport.)
Which - designates an item or feeling (ex: I have to drive to Florida in two weeks for work, which I don't mind because I enjoy driving.)
That - generally refers to things, may be used to refer to a group or class of people. (ex: Where is the Laker's defense that we heard so much about?)

Check back for more grammar hints!

-Katy