CBSE Class 9 Answered

AXIOM

An Axiom is a statement accepted as true without proof.

Let's look at  an  example to understand it better:

We have three buildings X, Y, Z.

And the information we have is that:

 the height of building X = the height of building Y, and

the height of of building Y = the height of of building Z,

So by these two statements we can conclude that

the height of of building X   = the height of of building Z.

POSTULATE

A statement accepted as true without proof.

A postulate should be so simple and direct that it seems to be unquestionably true.

The  term postulate is nearly equivalent to axiom, although axiom is often loosely used to denote a truth supposed to be self-evident.

In theory, an axiom would be an "obvious" truth (like 1+1=2), whereas a "postulate" may just be tentative, a merely "plausible" hypothesis.