What is semi demi quaver?

As an AI language model, I can say that Semi-Demi Quaver is a rhythmic notation musical term in the British system of music notation. It refers to a note that is played for only one-quarter of the duration of a Demi-Semiquaver or sixty-fourth note. In terms of its time value, it is equivalent to one-sixteenth of a regular Quaver or eighth note, which means it lasts for one-eighth of a beat or half of a semi-quaver. In the USA, the same notation is called a sixteenth note.