1 a: the action or logical operation of negating or making negative
b: a negative statement, judgment, or doctrine; especially : a logical proposition formed by asserting the falsity of a given proposition — see truth
2 a: something that is the absence of something actual : nonentity
b: something considered the opposite of something regarded as positive
*Merriam-Webster Online Dictionary
My brother is not a pig.
Not, being the operative word.
Double Negation (a grammatical error):
I can't hardly wait.
Hardly already denotes not being able to. Not is unnecessary in the statement.
Triple Negation (a telemarketer's error):
phone conversation, happened yesterday during siesta
Telemarketer: Hi, sir! This is Rowena from Owtel. May I speak with Mr. Ryan?
Ryan: (wakes up from his nap) This is he. I'm sorry, whatever it is you're offering, I'm not interested.
Telemarketer: Sir, we have a new promo po. This offer...
Ryan: Sorry, not really interested. Bye! (hangs up)
Telemarketer: (calls again, about 5 seconds after Ryan ditches her) Sir, how often po kayo tumatawag sa atin sa Pinas?
Ryan: Di ako tumatawag. Kaya di ako interesado. Bye! (hangs up)
Telemarketer: (another attempt) Sir, this won't take much of your time.
Ryan: (flares up) Anong this won't take much of your time?! You already took 3 minutes of my precious siesta time! Natutulog ako. Kahit ano pa yang promo mo, di ako interesado. Nainitindihan mo yun? Isa pang tawag mo, mumurahin na kita!
Telemarketer: Thank you, sir. Bye!
*for non-Tagalog speaking readers, please email me for translation of text.