Wisdom from the Early Stoics, Zeno of Citium 41

There is a difference between judgement, interrogation, and inquiry, as also between imperative, adjurative, optative, hypothetical, vocative, whether that to which these terms are applied be a thing or a judgement. 

For a judgement is that which, when we set it forth in speech, becomes an assertion, and is either false or true.

An interrogation is a thing complete in itself like a judgement but demanding an answer, e.g. "Is it day?" and this is so far neither true nor false. 

Thus, "It is day" is a judgement; "Is it day?" an interrogation. 

An inquiry is something to which we cannot reply by signs, as you can nod Yes to an interrogation; but you must express the answer in words, "He lives in this or that place."

An imperative is something which conveys a command: e.g.

Go thou to the waters of Inachus.

An adjurative utterance is something . . . A vocative utterance is something the use of which implies that you are addressing someone; for instance:

Most glorious son of Atreus, Agamemnon, lord of men.

A quasi-proposition is that which, having the enunciation of a judgement, yet in consequence of the intensified tone or emotion of one of its parts falls outside the class of judgements proper, e.g.

Yea, fair indeed the Parthenon!
How like to Priam's sons the cowherd is!

There is also, differing from a proposition or judgement, what may be called a timid suggestion, the expression of which leaves one at a loss, e.g.

Can it be that pain and life are in some sort akin?

Interrogations, inquiries and the like are neither true nor false, whereas judgements or propositions are always either true or false.

—Diogenes Laërtius, 7.66-68