Aposiopesis ( /ˌæpəsaɪ.əˈpiːsɪs/; Classical Greek: ἀποσιώπησις, "becoming silent") is a figure of speech wherein a sentence is deliberately broken off and left unfinished, the ending to be supplied by the imagination, giving an impression of unwillingness or inability to continue. An example would be the threat "Get out, or else—!" This device often portrays its users as overcome with passion (fear, anger, excitement) or modesty. To mark the occurrence of aposiopesis with punctuation an em dash or an ellipsis may be used.
A classical example of aposiopesis in Virgil occurs in Aeneid 2.100. Sinon, the Greek who is posing as a traitor to deceive the Trojans into accepting the Trojan Horse within their city wall, tells about how Ulixes spread false rumors at Sinon's expense. Indeed, Ulixes does not stop his malicious gossiping until he causes Sinon's ruin with the help of the seer Calchas. The whole story is a lie that Sinon tells with consummate artistry in order to convince the Trojans that he deserted the Greeks to escape Ulixes's enmity. To ensure the effect of his elaborate lie, Sinon at one point leaves a crucial statement unfinished (Aen. 2.97-100):
hinc mihi prima malis labes, hinc semper Vlixes
criminibus terrere nouis, hinc spargere uoces
in uulgum ambiguas et quaerere conscius arma.
nec requieuit enim, donec Calchante ministro—
This was the time when the first onslaught of ruin began for me.
Ulixes kept terrifying me with new accusations,
kept spreading ambiguous rumors among the people,
and kept looking for quarrel.
Nor did he in fact ever stop, until with the help of Calchas—
A more modern example of aposiopesis occurs in Mark Twain's Tom Sawyer: “Well, I lay if I get a hold of you I'll—.”
A biblical example is found in Psalm 27, verse 13. In English it says: "Unless I had believed I would see the goodness of the Lord in the land of the living . . . " The implication is that the author does not know what he would have done.
In syntax, an aposiopesis arises when the 'if- clause' or protasis of a condition is stated without an ensuing 'then- clause' or apodosis. Because an aposiopesis implies a trailing off of thought, it is never followed by a period, which would effectively result in four dots.