Definitely

It's a word that I use fairly often, but not all time.  I prefer saying "definitely" rather than saying "yes."  I know in the south it is considered "polite," to say, "yes, ma'am" and "yes sir," but I had teachers that didn't like that and parents from California, so I never really said "yes, ma'am" or "yes sir."  I also never said "no ma'am" and "no sir" for the same reasons.

Sometimes saying "ma'am" or "sir" made people feel old. Other times, the teachers or parents didn't like the way it sounded because it would sound like other words or just sound strange to that person.

Anyway, with my mom and sister having Asperger's and having it difficult at other times for people to catch a one syllable word, "definitely" works better than "yes" because then the word "no" is the only one syllable word. 

Sometimes I say "negatory," but I usually don't.  At least it would still be easily distinguishable from "definitely."

Of course, sometimes I still say "yes."  The word "yes" isn't banned from my vocabulary.  I've simply found that a word that is longer than "yes" usually works better for people to understand. I still say "yes" when a short or quick answer is needed.

I also use "definitely" with the correct usage unlike how many people use "literally."  After all, if a person "literally dies" that means the person is dead. 

The Oatmeal has a great cartoon about the usage of the word "literally."

See The Oatmeal's literally cartoon.