1. The diacritical mark: This is the most common meaning, referring to the two dots placed over a vowel to indicate a separate pronunciation (like the "ü" in "über"). This is the same as the English word "diaeresis".
2. A medical term: It can also refer to a tremor, which is an involuntary, rhythmic muscular contraction. This meaning is less common than the first.
So, depending on the context, "tréma" could be translated as either diaeresis or tremor.