abstract is a concept or relationship that applies to more than one specific type of subjects.

for example, 1+1=2 is an abtract. It applies to 1 apple+1 apple = 2 apples the same way it applies to 1 car+1 care = 2 cars. Abstract then can be at different levels, though. For example, algebra is a higher level abstract compared with arithmatics. In a+a=2a, a can be 1, 2, or -1, etc. I believe that human’s intelligence must be limited to certain level of abstract. Beyond that, the abtract still exist, but we as human won’t see it. those things take so-called ‘faith’ to apprehend.

obtaining functionality from experience instead borned with or pre-programmed. this applies to human, animals, machines – or as a matter of fact, any ‘things’, say, plants. though this question is oftened asked in the context of machine learning