irony
in
The Devil's Arithmetic

when what happens is very different than what might be expected; or when things are together that seem like they don't belong together -- especially when amusing or an entertaining coincidence

This is sometimes referred to as "situational irony."  The term is especially appropriate when actions have consequences opposite to those intended.

The expression ironic smile, generally references someone smiling at situational irony.

All forms of irony involve the perception that things are not what they might seem.

saying one thing, while meaning the opposite or something else -- usually as humor or sarcasm

(With this type of irony, it's not uncommon for the words to say one thing while the tone-of-voice and/or context says another.)

This is sometimes referred to as "verbal irony."

All forms of irony involve the perception that things are not what they are said to be or what they might seem.

when the meaning of a situation is understood by one person, but not by another -- especially when a reader or audience knows what characters of a story do not (such as in the play, Romeo and Juliet)

All forms of irony involve the perception that things are not what they are said to be or what they seem.

meaning too rare to warrant focus:

Less commonly, Socratic irony is where someone pretends ignorance to get another to think through a problem. This is named after the Socratic method of teaching.

Less commonly still, some also refer to romantic irony as when an author reminds the audience that the fictional words is the author's creation and will play out as the author desires.