There's no clear definition of what OO is, so the best you can do pragmatically is look at mainstream languages that are broadly recognized as OO and try to deduce the commonalities.
If you do that, you'll notice that, for example, encapsulation is not a part of that de facto definition, because languages like Python and (until recently) JavaScript lack it, despite being considered OO.
Indeed, the only two things that appear to be consistently present in all OO languages are: 1) some notion of object identity as distinct from object state, and 2) runtime polymorphic dispatch.
If you do that, you'll notice that, for example, encapsulation is not a part of that de facto definition, because languages like Python and (until recently) JavaScript lack it, despite being considered OO.
Indeed, the only two things that appear to be consistently present in all OO languages are: 1) some notion of object identity as distinct from object state, and 2) runtime polymorphic dispatch.