Diminished Third: A diminished third is an interval that spans two whole steps or four half steps. It is even larger than an augmented second and has an extremely dissonant sound.
Tritone: The tritone is an interval of three whole steps or six half steps. It divides the octave into two equal parts and has a very unstable and unresolved sound.
Enharmonic Equivalents: Enharmonic equivalents are different notations for the same pitch. For example, C# (C sharp) and Db (D flat) represent the same pitch but are written differently depending on the context or key signature.