What is the Question?
The question may seem clear: whether there is a word that indicates something that lies between the abstract and the concrete. However the example given — ‘violence’ — does not seem to have that attribute, and I find the explanation of why the poster considers ‘violence’ as neither abstract nor concrete difficult to follow, especially as he does not contrast this word with ones he considers truly abstract or concrete. If people have different understandings of what the word means, why does he think the majority of people recognize ‘violence when it is occuring’ — or what does he mean? Does he mean that if people see the same video of someone thumping someone else most will regard that as violence, of does he mean that each of us well recognize what we individually regard as violence — some only physical abuse, some also verbal abuse, others also psychological abuse?
In view of this lack of clarity, I now regret having shot off a few suggestions regarding one simple interpretation of the question, as this has drawn a comment that now makes me feel obliged to try to provide a more comprehensive answer. And me only a biological scientist with a profound distrust of philosophy. Fools rush in…
Is there an Answer?
First, I do not think ‘violence’ (or indeed any concept) is a true intermediate between concrete and abstract. Let us consider examples of the two. I’m not sure that words themselves are either concrete or abstract — they are abstract in the sense that they exist in the mind, they are concrete in that when spoken you can hear them. But, agreeing to call them concrete or abstract for the ideas they describe, I suggest that something like ‘football’ is a concrete word as it describes something you can recognize and hold, and ‘beauty’ is an abstract word because it describes a response of the senses. It seems important not to confuse this distinction with precision or ambiguity, because both of these terms mean different things to different people. When I pick up a football it will be spheroidal, whereas for others it will ovoidal, and, of course, beauty is in the eye of the beholder. So, to me ‘violence’ is either a concrete word like ‘homicide’, or an abstract one like ‘evil’.
A more sophisticated consideration of this question can be found elsewhere in SE ELL, as pointed out by @EdwinAshworth.
However, if one must use a word to express the idea of an intermediate between abstract and concrete — given that none appears to be in use — I will borrow one from science:
Biology on Line defines this as follows:
“Amphipathic is a word used to describe a chemical compound containing
both polar (water-soluble) and nonpolar (not water-soluble) portions
in its structure.”
(Merriam-Webster redirects to ‘amphiphilic’, more used in the physical sciences, but less appropriate here.)
Although used in a specific chemical sense, the derivation from amphis (both) and pátheia (feeling) does not include any specific chemical reference, making the term eminently suitable for application in other spheres.
And an answer to the alternative interpretation of the Question?
However, perhaps the example given by the poster falls into one of the following categories, for which adjectives to describe the concept of violence (“The word violence describes a ........ concept”) are given:
Lack of definition of what the word means
not easy to see or understand
capable of being understood in two or more possible senses or ways
having no definite form
The meaning is still in flux
subject to change or movement
imperfectly formed or formulated
The word can be construed in different ways
capable of adapting to varying conditions