Zip! Zero! Nada!
The absence of anything. Not a thing. What could be simpler and more straightforward? Actually, it's pretty complicated. Nothing is seldom really nothing.
You would think that they could at least get it straight in mathematics. One of the first things they teach you is that zero is nothing. Simple as a pimple, right? But as soon as you grasp that concept, they tell you that you can have less than nothing. Huh! So "nothing" must really be something, simply because it's greater than less than nothing. Still gives me a headache trying to figure it out.
And forget about physics. Physicists, in attempting to calculate the mass of the universe, are quite determined to prove that "nothing" must really be something, since they can't find enough "something" to add up to what they consider to be everything. Confusing? Irrational? Just remember that these are the same folks who say that nothing can exist in a vacuum. Guess they never emptied one.
The Nihilist considers everything to be nothing, while many Buddhists think that achieving nothing is everything. And, if you're the irreverent type, nothing is sacred.
If you're religious, you believe that God created everything out of nothing. If you're a taxpayer, you are constantly amazed at the ability of our politicians and bureaucrats to create "nothing" out everything you worked so hard to earn.
And isn't it odd that where you have your "nothing" is important?
Anybody else got nothin'?