# Thread: What is the difference between not a or b and not a nor b...??

1. ## What is the difference between not a or b and not a nor b...??

as written above... I am confused to know about that...

2. ## Re: What is the difference between not a or b and not a nor b...??

Welcome to the forum, evessc.

It would help if you could give us some sentences as examples of the words you are asking about being used.

3. ## Re: What is the difference between not a or b and not a nor b...??

Originally Posted by evessc
as written above... I am confused to know about that...
Symbolic logic is at issue here.

"¬" (negation) is a basic logic symbol; so is "∨" (logical disjunction) and "^" (logical conjunction).

not a or b (with logical opetrator notation) = ¬A∨B

A ¬A B ¬A∨B
0 1 0 1
0 1 1 1
1 0 0 0
1 0 1 1

not a nor (=and not) b (with logical opetrator notation) = ¬A ^ ¬B

A ¬A B ¬B ¬A ^ ¬B
0 1 0 1 1
0 1 1 0 0
1 0 0 1 0
1 0 1 0 0

You can see the difference now.

4. ## Re: What is the difference between not a or b and not a nor b...??

Originally Posted by Ilki
Symbolic logic is at issue here. [...]
You can see the difference now.
Unfortunately for this idea, native speakers do not always follow the rules of formal logic when they speak; sometimes, perfectly acceptable utterances defy logic.

This is why logicians use symbols.

5. ## Re: What is the difference between not a or b and not a nor b...??

Originally Posted by 5jj
Unfortunately for this idea, native speakers do not always follow the rules of formal logic when they speak; sometimes, perfectly acceptable utterances defy logic.
I agree. Could you come up with an example? My hazy brain can't think of any at the moment.

6. ## Re: What is the difference between not a or b and not a nor b...??

Originally Posted by Ilki
Could you come up with an example? My hazy brain can't think of any at the moment.
An indirect condition occurs when there is a logical gap in the overt meaning between the two parts of a conditional sentence. For example, the stated outcome in the following does not depend on the fulfilment of the if-clause;

You look tired, if you don't mind my saying so
If you're going in July, it will not be raining

Chalker, Sylvia and Weiner, Edmund(1993.83-4) The Oxford Dictionary of English Grammar, 2nd edn, Oxford: OUP

7. ## Re: What is the difference between not a or b and not a nor b...??

Originally Posted by Ilki
I agree. Could you come up with an example? My hazy brain can't think of any at the moment.
An important issue here (not the only one) is the use of parentheses. We do not use parentheses in natural languages the way we do in formal languages. We have an example in this thread.

not a or b

Is it

(not a) or b

or

not (a or b)

?

You chose one interpretation, which was different from mine. Both are equally valid because English has no means of distinguishing between them without changing the wording.

8. ## Re: What is the difference between not a or b and not a nor b...??

Originally Posted by evessc
as written above... I am confused to know about that...