Epstein's logic terminology I am reading Classical Mathematical Logic by Epstein. I am a little bit unclear on some of his terminology:

No [abbreviated] wff such as $p_0 \wedge \neg p_1$ is true or false; that is the form of a proposition, not a proposition. (Page $11$)



A formal wff is true oe false in the model according to whether its realization is true or false. (Page $17$)

If we are given a certain realization and its valuation:
$p_0 =$ the sky is blue (True), $p_1 = $ iron is red (False) 
Is $((p_0) \wedge (\neg (p_1)))$ a proposition? Or is it just a statement that happens to be false (as per the second quote) , but it is not a proposition?
Say, the variables are realized, but they are not valuated. Is $p_0 \wedge \neg p_1$ a proposition then?
Edit:
Epstein defined as follows:
Proposition: "A Written or uttered declerative sentence used in such a way that it is true or false, but not both."
Realization: "A realization is an assignment of propositions to some or all of the propositional variables. The realization of a formal wff is the formula we get when we replace the propositional variables appearing in the formal wf with the propositions assigned to them; it is a semi-formal wff. The semi-formal language for that realization is the collection of realizations of formal wffs all of whose propositional variables are realized. "
Valuation: " We agree that sentences assigned to propositional variables...are propositions... But it is a further agreement to say which thruth-value it has. When we do that we call all the assignments of specific truth-values together a propositional valuation, $v$, and write $v(p) = T$ or $v(p) = F$ according to whether the atomic proposition $p$ is taken to be true or false.
 A: $p_0\wedge\neg p_1$ is not a proposition, merely a construction of logical operators and variables, as by the first quote. The realisation (sky blue and iron not red) turns this construction into a statement, but it is neither true nor false, as at this point we do not have the truth value the expression should evaluate to. The original expression is also neither true nor false, by the second quote.
Such wffs get turned into propositions by equating them with a single truth value: $p_0\wedge\neg p_1=0$, $p_0\wedge\neg p_1=1$ ("sky blue and iron not red" is true/false). The realisations of these are statements that can be assigned true/false values: if I am on Earth, the sky is indeed blue and iron not red, so $p_0\wedge\neg p_1=1$ is a true proposition, and its realisation a true statement. If I was on Titan, where the atmosphere is orange, $p_0\wedge\neg p_1=1$ would be a false proposition and its realisation a false statement.
A: From the definitions given (which are not formal enough to be precise), I guess that he considers any well-formed formula made from connecting atomic propositions as a proposition too.

If $p_0,p_1$ are formulae then "$p_0 \land \neg p_1$" is also a formula.
If $p_0,p_1$ are propositions then "$p_0 \land \neg p_1$" is also a proposition.
If $p_0,p_1$ are true in some world then "$p_0 \land \neg p_1$" is false in that world.

The second point means that the string "$p_0 \land \neg p_1$" is not a proposition, but the string "( the earth is flat ) $\land$ $\neg$ ( the moon is made of cheese )" is a proposition but still has no meaning or truth value whatsoever until it is interpreted in some world.
Note that this is my best guess and there may be deviation from the intended meaning of Epstein. Normally in formal logic we do not have the second level because it's simply a second language that is essentially no different from the first (propositional language). After all, we can directly interpret the string "$p_0 \land \neg p_1$" in a world simply by specifying the interpretation of $p_0,p_1$ in that world.
