How do you call something thats true that can't be proven?

Question

example 2+2=4 everyone knows that but it con't be proven everyone just agree with it....

Answer 1

Not sure. You could be looking for axiom or conjecture.

Conjecture means:

A conjecture is something which is generally believed to be true but has not been proven (or disproven). One website calls it "an educated guess"

An unproven statement that is based on observations.

A hypothesis drawn from observed patterns in several examples

A conjecture is a statement which, although much evidence can be found to support it, has not been proved to be either true or false

Axiom means:

An axiom is a proposition that is not proved or demonstrated but considered to be self-evident. Therefore, its truth is taken for granted, and serves as a starting point for deducing and inferring other (theory dependent) truths. -Wikipedia.

A proposition that is not susceptible of proof or disproof; its truth is assumed to be self-evident

A self evident principle or fact.