(adjective)
existing as an idea, expression, feeling, or quality and not having physical or concrete existence as a solid object;
e.g. According to philosophers, perfection is an abstract concept that can never be realized.
(verb)
to extract or remove (from the whole, or from the context): to consider something theoretically or separately from something else;
e.g. Let's abstract our emotions from this situation, and try to focus mutually on how we can move forward together.
(noun)
a summary of the key points of something, sometimes informally or sometimes in a highly stylized written format, as a scientific abstract of research;
e.g. The abstract he wrote of his research into glucose metabolism was accepted by a prestigious scientific journal.
(verb)
to make a written summary of the points of something else, for instance, research, or an argument, or a book, usually presented in a skeletal form, and sometimes in a highly stylized, specific writing form;
e.g. The class was instructed to abstract the key points of each article in the five scientific journals.