[This is a lesson excerpt from our online course, for which we invite you to enroll.]

Think you know what the word "or" means? You might not! Check out this video to find out more about one of our favorite LSAT fundamentals.

“OR” is a Very Confusing Word In English

The word OR on the LSAT

Do you know really what this word means?

The word “or” and the often interchangeably used phrase “either or” are ambiguous. That means they have more than one meaning. Sometimes “or” means “or, but not both,” sometimes it simply means“and,” and sometimes, it means “and/or.” Context will tell you which meaning is intended and let me save you a lot of trouble and tell you right now that the meaning that the LSAT summons most often is “and/or.” That’s why we included “or” as a Group 3 logical indicator.

Now, let’s take a look at two of the three different meanings of this confusing word.

(1) You may sit either at one end of the table or the other end.
(2) Jane is a faster eater than either Mary or Jon.

The “either or” functions differently in those sentences.

For sentence (1) the “either or” says that you can get to have one possibility, at the exclusion of the other possibility. You may sit at one end of the table, or you may sit at the other end, but certainly you cannot sit at both ends of the table. We call this is “exclusive or.” We’ll revisit this interpretation of “or” when we cover bi-conditionals in a later lesson.

For (2) the “either or,” as opposed to being exclusive, is demandingly inclusive. So much so that Jane is not just a faster eater than Mary but slower than Jon. Nor is she just a faster eater than just Jon but slower than Mary. Nope. Jane lays waste to her hamburgers and fries faster than Mary and faster than Jon. We call this the “and.” It’s odd, I know. The word “or” means “and” when used in this context.

Consider a third sentence.
(3) Jon must enroll in Economics or Political Science this semester.

Some of you will think that Jon is taking one class at the exclusion of the other. Others of you may disagree, i.e. you think that Jon is taking both classes. Who’s right? Both, possibly. The fact is, we don’t know what classes Jon is taking. According to this sentence, he must take at least one of the two classes. That much is certain. But, he could take both. We call this this “inclusive or.” This is the “or” that we included in our Group 3 logical indicators.

Or is confusing. Remember the rule of thumb is to read “or” like in sentence (3), i.e., the inclusive usage of the word.

Here is a useful way of thinking about “or.” First, you have to figure out which meaning is intended. If it’s meant to be read as “and,” then that’s easy. Read it as “and.” If, however, it’s meant to be read as “exclusive or”, i.e., “one or the other, but not both,” then just understand that of the two, you have to choose at least one and at most one. In other words, you have to choose exactly one. For example, if we say “you must eat either the steak or the cod, but not both.” You have to eat at least one of steak or cod and not both steak and cod. That means you eat exactly one of the two, no more, no less.

Now, on the other hand, if the “or” is read as the “inclusive or,” i.e., you have to choose at least one, but you could have both, then, you should think about it this way: The minimum I need to choose is 1, but the maximum is 2. For example, reference sentence (3).

“Or” and “either or” are confusing. They have 3 different meanings. (1) the “exclusive or”; (2) straight up “and”; (3) the “inclusive or.” Context will determine which meaning is intended.

Did this lesson help you understand the word OR? Let us know in the comments, and check out our online LSAT course for more lessons like this.