Which is what most people think when they say "inheritance".

There's also interface inheritance. Delegation is yet another different thing that uses prototyping and on-the-fly "inheritance" graphs. Inheritance is really just one-way static delegation (and I won't get into categories here :-).

But to answer your question, most OO definitions include inheritance. Languages without inheritance are often called "object-based". Read 1.15, 1.4, and 1.7 [link|http://www.cyberdyne-object-sys.com/oofaq2/|here] for more.