this is some questions that I replied to many years ago on dsg
1) How is concept specifically different from vitakka?
Vittaka is a paramattha dhamma. The usual translation is applied thinking. Howeer it is not exactly the same as what we usually meaqn by thinking. Even when we are in deep, dreamless sleep vittaka arises. Nevertheless we can say it is or may be predominant when we are thinking (in the conventional sense). When we are thinking about some idea one of the dhammas that is arsing and passing away during those moments is vittaka. If sati of satipatthana takes vittaka as an object, or any other dhamma, then the concept will disappear for the moments that this is happening. This is because sati, of this type, only takes paramattha dhamma for object.
2) Is there a pali word for concept?
Pannatti is the pali for concept. As Acharn Sujin explains in 'Realities and concepts' there are different types of concept. Such words as dosa, lobha, metta, colour, hatred, sound are concepts that designate paramattha dhammas, they are vijjamana pannatti. Words such as person, animal, computer, Robert, Mike do not refer to paramattha dhammas and are called avijjamana pannati.
3) Doesn't a concept arise at the mind-door?
Concepts are dhammarammana(mental object) and they appear at the mind-door. The mind-door has many different objects including citta, cetasika, rupa and nibbana which are all paramattha dhamma. It also has concept as an object.
4) Is it not taken as an object by citta?
Yes but not in the same way that paramattha dhammas are taken as object. How could it as it is not real. The cittas and cetasikas are arising and passing away at great speed and forming up concepts but these concepts have no existence, although they give the illusion of existence. It is so hard to talk about this -- we are using concepts to discuus it-- and yet this is all happening right now. Can we see it? By the development of satipatthana the difference between concept and paramattha dhamma must gradually becomes clearer. Now you are reading this so it might be worthwhile analysing what is actually happening. There is visible object, the different colours making up the computer screen. The colours are real (but arising and passing away rapidly) the computer screen is not real, however the various rupas that make up the screen are real,(and arising and passing away ceaselessly). There is cakkhuvinnana, seeing consciousness which is real (and ephemeral) which arises due to the contact of the eyebase (real, conditioned by kamma done in the past, evanescent). Then there are processes of citta which experience the same object and then there are mind-door processes which think about what was seen and so concepts are formed up. Yet these concepts do not actually exist. There must be this process occuring, no one can stop it occuring. If it didn't occur we would be utterly vacuous, know nothing at all, much less than a new born baby. Thus it is the most natural thing that concepts arise.
Unfortunately, though, throughout samasara we have given these concepts special staus that they don't deserve, namely we think they exist. This mistaken notion means that we will do all sorts of evil to protect these illusionary figments such as self. When we see that concepts are simply concept, and that even parammattha dhammas are so temporary, would we still get so upset when we are critisised? Would we hate the man who steals our wife once we know that both are only idea? I think we would not kill, steal, lie or cheat over distintergrating colours, sounds or tastes. We can only get angry because of the distorted vision that can't fully penetrate these matters. Thus papanaca and mannati are working.
5) Can someone please cite a clear, direct instruction on this topic from the sutta-pitaka?
The Buddha said that the all includes the 6 doors and there objects and the sense bases. There are many suttas classifying dhammas in different ways, the ayatanas, the khandas, the dhatus, so that they can be understood, so that concept is not mistaken for paramattha dhamma. The satipatthana sutta elucidates different dhammas that can be insighted. Anger is one of the objects listed in the satipatthana sutta- it should be understood. When we are angry do we see that we are angry with an illusion? Do we understand that what is really happening is simply cittas arising and passing away that are roooted in dosa. By studying our "lives", which are only these brief moments of anger and lust and doubt and fear and pleasure and pain, and seeing, hearing, tasting, touching, by applying the satipatthana sutta, we are beginning to separate paramattha dhamma from concept.