To me they sound like the same thing.

A or B means to be in either the set of A or B. While A and B means being in both A and B, i.e. the set that is the intersection of the sets.

Results 1 to 13 of 13

- January 15th 2011, 06:05 PM #1

- Joined
- Sep 2009
- Posts
- 158

## Either A or B

I've had enough.

So what does Either A or B mean? (I've been taking it to mean the inclusive or)

What does A or B mean? (I've been taking this to mean the exclusive or)

I see people using both interchangeably, and it is nothing short of frustrating. Is there a mathematical convention that dictates how to use the above statements and how to interpret their use?

- January 15th 2011, 06:15 PM #2

- January 15th 2011, 06:24 PM #3

- Joined
- Sep 2009
- Posts
- 158

- January 15th 2011, 10:15 PM #4

- January 15th 2011, 10:25 PM #5

- Joined
- Sep 2009
- Posts
- 158

- January 15th 2011, 10:27 PM #6

- Joined
- Mar 2010
- From
- Florida
- Posts
- 3,093
- Thanks
- 8

- January 15th 2011, 10:44 PM #7

- Joined
- Sep 2009
- Posts
- 158

- January 15th 2011, 10:46 PM #8

- Joined
- Mar 2010
- From
- Florida
- Posts
- 3,093
- Thanks
- 8

- January 16th 2011, 11:11 AM #9

- Joined
- Sep 2009
- Posts
- 158

You do realize that every such articles write... "and oh by the way Either... or means the inclusive or, but sometimes it means the exclusive or"

I was just hoping that someone would have a link to a set of guidelines for mathematical writing to which everyone adhered so that I wouldn't have to go crazy every time a definition or theorem was given using the either...or combination

- January 17th 2011, 07:15 AM #10

- Joined
- Apr 2005
- Posts
- 17,719
- Thanks
- 2266

- January 17th 2011, 07:35 AM #11
In his

__Symbolic Logic__textbook, Copi points out that there are two words in Latin for*or*,and**vel**.**aut**

The wordmeans**vel****or**the inclusive sense, at least one is true.

The wordmeans**aut****or**the exclusive sense, one is true but not both.

Copi maintains that we get the symbol that we use for**or**, , from the first letter of. Therefore, in logic we use the inclusive meaning.**vel**

- January 17th 2011, 03:22 PM #12

- Joined
- Sep 2009
- Posts
- 158

__V__Is the exclusive or... these are just definitions... and they're easy. But not all textbooks are written in logic, they're often written in a "slightly" less logical language called english. Sorry, I think I may be coming across as hostile, and it's not my intention.

- January 17th 2011, 03:38 PM #13
I don’t find you hostile, just frustrated.

In my lifetime I have had to learn three different systems of logical notations. So I more or less understand.

BTW. The notation for the exclusive or is really relatively new.

It appears nowhere in Copi’s texts.