Contradiction! Any Symbol for?

Solution 1:

Different sources use different symbols (if they use symbols at all). I've seen $\Rightarrow\Leftarrow$ most often. For some others, see "Symbolic Representation" here.

Solution 2:

I am surprised to see that nobody has mentioned $\bot$. In logic, this is a standard symbol for a formula that is always false, and therefore represents a contradiction exactly.

In almost all logical formalisms, one has a rule of inference that allows one to deduce $p$ from $\bot$ for any $p$ at all, and it is usually possible to prove that $(p\land\lnot p)\to \bot$ and so forth.

Solution 3:

The symbol I've seen most commonly in mathematical logic statements is also the one which was taught to me in a class called "Discrete Mathematics;" it is something like a sideways number sign or "pound sign" (or "hashtag," as some might call it today).

Solution 4:

Some of my teachers and I use someone like (Harry Potter's scar) this $\unicode{x21af}$ (LaTex: \unicode{x21af})

Solution 5:

I always had used the following notation. At least in my academic environment this one was suggested and used. You can also see these links

• Wikipedia (The part "Symbolic representation").
• TeX (The first page of the section "3 Mathematical symbols").

They both has brought this symbol among symbols that are common for contradiction. About how to type it in TeX with better size, see this link.