“Consciousness. 1 a: the state or fact of being conscious of an external object, state, or fact.”
The definition above gives what philosophers call “intentionality” a key role within consciousness. Intentionality is basically about how consciousness is directed outwards towards external objects, events, etc.; or inwards towards mental states, emotions, images, thoughts, etc. (Intentionality can also be called directedness or aboutness.)
As you can see, this definition may be seen as a characterisation of a property of consciousness; rather than a characterisation of consciousness itself. Despite that, we can solve that problem by saying the following:
The very awareness of external objects, etc. constitutes consciousness.
This means that instead of “predicates of consciousness”, we have a partial “is of identity” here:
intentionality = (or is partly constitutive of) consciousness
Nonetheless, some philosophers may see this distinction between consciousness and its properties/functions as being bogus. It may not make much sense to characterise consciousness other than by mentioning its various properties. Daniel Dennett, for example, also takes a parallel (see my 'On Definitions of “Consciousness”: Dennett and Others') position in that he argues that consciousness simply is the set of properties (e.g., functions, processes, behaviour, overt speech, etc.) which we call 'consciousness'.
In opposition to that view we have those philosophers who stress consciousness “as it is in itself”. They talk about “qualia”, “phenomenal properties”, “what it is like”, etc. However, can't these things also be seen as properties of consciousness rather than being consciousness itself? Again, perhaps this simply shows us that we're searching for a ghost (“in the machine”?) when we discount all these so-called properties of consciousness. That is, we may be treating consciousness as what philosophers once called a “substance” (or, perhaps, a Kantian noumenon).
In any case, there's a contemporary position on this debate that's worth mentioning here. This is the position called “phenomenal intentionality”. Here is a broad account of this position:
“While many contemporary theories of intentionality attempt to account for intentionality in terms of causal relations, informational relations, functional roles, or other 'naturalistic' ingredients, PIT aims to account for it in terms of phenomenal consciousness, the felt, subjective, or 'what it’s like' (Nagel 1974) aspect of mental life.”
Even here I suspect that all we have is old philosophical ground which has been re-christened with a neologism (or Derrida's 'sign-substitution') – i.e., “phenomenal intentionality”. Nonetheless, that doesn't stop it from being old ground with a (slightly) new emphasis.
“1 b : the quality or state of being aware especially of something within oneself.”
The notion of intentionally is continued in this part of the Merriam-Webster definition.
In this case it's said that consciousness is “being aware especially of something within oneself”. This can be deemed to be internal intentionality in that this “something” is “within oneself”. In other words, there's no reference here to external objects/events/conditions/facts/etc.; or even to any mental “representations” of external things.
It can also be argued here that these are higher-order descriptions of mental states which incorporate both a notion of a self and what's called self-consciousness. In addition, a human subject can be conscious of an external object (or an internal thought/emotion) and also be aware that he or she is so.
In this case, self-consciousness needn't necessarily about a self as a “substance”. In David Hume's book, for example, the self is simply whatever occurs within a person's mind or what "runs through" his or her consciousness (i.e., as long as there's some kind of “awareness” of what runs through the consciousness). It can be said that most animals don't have this higher-order capacity. Nonetheless, do human animals always need to be aware (however that word is cashed out) of their consciousness of an external objects and internal states? Or are these things higher-level additions to consciousness?
“2: the state of being characterized by sensation, emotion, volition, and thought.”
This part of the Merriam-Webster definition appears - on the surface - to bring on board what philosophers call qualia. Or, at the least, it adds sensations and “how things feel” into the pot. In opposition to the intentionality mentioned above, there's no reference here to external objects, states or facts. Nonetheless, when a human subject is conscious of such things, then that may also include sensations, emotions, etc. However, such mental states or properties aren't themselves representations of – or about - objects, states or facts; and neither are they, strictly speaking, thoughts.
Thus when one is conscious of the flowers in a garden, one will also be aware of all the colours and smells of those flowers. The colours and smells are (as it were) over and above the flowers in the garden. And just as flowers have the properties of colour and smell, so one's consciousness of those flowers will made up of sensory properties (or qualia). However, various kinds of philosopher and scientist (from idealists to realists) may question that bifurcation between the properties of flowers and the properties of those consciousness states which are of (or about) the flowers. This has been called “the phenomenological fallacy”. (There is also a parallel - ontological - question about the bifurcation between properties and the objects which have properties.)
In addition, that consciousness of a flower garden may be accompanied by an emotion; which is also above and beyond the conscious representation itself. Therefore what are called the “intentional objects” of consciousness (flowers in this case) are fused with emotions or feels; which can themselves be described as - or broken down into - qualia.
This total package-deal of consciousness is the subject of part 3 of this definition:
“3: the totality of conscious states of an individual.”
Here it can said that even though conscious states (or a single conscious state) can be broken down phenomenologically, they can still be regarded as as wholes. In addition, perhaps it hardly makes sense to speak of a single mental state. This means that just as every part of a single mental state makes up a seamless whole; so each mental state is hardly distinguishable form both previous and forthcoming mental states. However, in terms of a philosophical (or phenomenological) analysis, it is indeed possible to break mental states down. This is done when a philosopher (as it were) circumscribes a single mental state and then describes – in words – what's often called (by philosophers) its “content”.