Citta, Mano, and Vinnana as Synonyms
An interesting point to be noted in SN 2.12.61 is the way the Buddha speaks of 'this very heart' (citta) or 'this very mind' (mano) or 'this very consciousness' (viññāṇa) as being synonyms for each other in essentially the same way we think about these things.
K. Nizamis argues in a footnote that the use here of these terms as we find them is not to be understood this way. That they are not to be understood as synonyms. And that this is an Abhidhamma interpretation. That being the case, I find myself for the first time agreeing with the Abhidhamma!
I do not say that these terms do not have specialized meanings. Indeed I have argued for translating them with terms that more precisely point out their differences than are currently used, but in the case we have here what the Buddha is talking about is the common way of understanding what we call our mind which various forms are all thought of as the same thing, that is 'mind'. Here to take Nizamis' understanding would be to warp the sutta and to miss the meaning which is not directing our attention to the precise forms of mind, but to the common understanding.
It might be better to understand all these things (including also 'sati') as 'ways mind works'. Some people see it one way or are of predominantly one form of it, some another, some a mixture, but the point of this sutta is that however it is experienced the common denominator is that it changes rapidly.
This is how I believe this matter should be seen: 'citta' is our 'heart' and means our mental center; mano is our 'mind' and has no discretely defined form or function or rather it has multiple meanings or serves as a unifying concept and can stand for the ordinary mind or the mind of the arahant; 'sati' is our 'memory' and is used as English 'mind' as in 'pay attention' and 'remember'; 'vinnana' is our 'consciousness' and is our knowing that we know and self-awareness. There are other terms as well that relate to functions we call 'mind': vimansa, investigation, vitakka and vicara, thinking, etc. All of these are the work of memory. What we consider the focus or center of our being is a consequence of the arising of memories; what we call our mind is a consequence of the piecing together of memories; what we call memory is the remembering of things; what we call paying attention is the remembering to notice what we are trying to remember to do. On top of the basic workings of memory, we apply views according to the use to which the memory is being put. When we want to remember how we feel about a thing we call it heart. When we want to think of ourselves as intelligent beings (man) we call it mind; when we want to use it to pay attention and recall things we call it memory; when we want to remember that we should stay awake when the Professor is speaking, we call it consciousness. They are all synonyms and they are not synonyms depending on the point you are trying to make.