I was wondering what the differences are between sleeper and dark horse.
Are they interchangeable while having similar meanings?
Are there other similar words?
From New Oxford American:
Here's some generalizations gleaned from the above:
As to your questions, I'd say they're not quite interchangeable. Knowing their different connotations will likely prove one to be the better word choice.
A dark horse might also be called an enigma, or simply an unknown; while surprise hit, cult classic, and box-office success are other phrases often applied to sleepers.
There are very slight differences. Usually they are interchangeable, however, "dark horse" has a nuance that "sleeper does not have.
In other words, a "dark horse" is someone who is expected to "not win", but a "sleeper" is just a person who wins unexpectedly, but no one has previously expected it to "not win".
"John wasn't well-known prior to this race. No one knew much about John, so they weren't sure John would win or not. It turns out that John did win. John is a sleeper."