Although all the above words have definitions, those definitions do not agree in the professional lexicon. So, in order to not be confused about 'real meaning' let's have a look at the 'blurred lines' and reach an agreement as set down within affectology.
First, I want to offer the text (in part) of a blog post, below, by Dr. Jeremy Dean. You can read this to see that the wider professional community is in a state of confusion over word usage, but please do so with some reservation. If you want to go straight to the definitive nomenclature that applies to our work and this site, start below at "The Affectology Perspective."
The Affectology Perspective
Because all variants of clinical affectology - Clinical Affectology, Af-x, ECR - rely somewhat on preparatory information that aids in us having a clearer picture of how the mind operates (before we can reframe or 'reboot' old encodings) and what 'territory' of mind we are bringing into focus, we have to settle on specific definitions.
As you can see from the above article, if we were to simply continue using words that are not clearly defined here, much misinterpretation is likely to occur. While we respect the varied views of 'emotion researchers' and their right to interpret words in whatever manner suits them and their work, it is essential for us to 'tighten' this issue so that we know what we're talking about in their use. To that end, we must adopt specific definitions that suit the affectology view-point. These may or may not be similar to the definitions of the 'researchers'.
Because 'science' and 'emotion researchers' have left us with a fuzzy box of words that seem to vaguely point in directions that are less than satisfactory, we must tidy that up and present a short vocabulary explicit to our needs.
In all things pertinent to our affectology view, please interpret the following words as being ...
Emotion: we favor the viewpoint that emotion, although enjoying a popular characterization as an umbrella term embracing all the words under examination here, really describes the symptom - the result - of more subtle unconscious core agents. So, emotion is a consciously recognized set of markers (somatic and psyche) that are the result of affect.
From an affectology stand-point, emotion refers mostly to recognizable moods and conscious feelings and reactions like anger, depression, anxiety, sadness, stress, and the like.
Feeling/s: while the affectologist is clear that the word 'feelings' is an ambiguous and wide-spectrum descriptor - used commonly to describe consciously registered emotion or mood - its use is uncommon in the affectology lexicon. To confuse matters even further, 'feeling' can be commonly used to describe somatic experience, as in "I'm feeling cold." This is not an overly useful definition in our case, as it lies well outside the focus pertinent to affectology. So, 'feelings' is not a commonly used word in affectology.
Core: In affectology, we use the word 'core' to refer to the inner unconscious matrix - the central feeling aspect of self that cannot be verbalized - that has been established before word use (preverbal) and carried over (perseverated) into adulthood. It is hidden (from the conscious mind), silent (exists in the form in which it was initially learned) and is an initiator of many of our characteristics as people and the way in which we react to the world around us, particularly in emotional (symptomatic) ways.
In practical (clinical) affectology we may refer to that 'inner affect self' as being the Emotional Core or Affect Core.