Depending on where your sheet music was printed, the same note wears a different name.
American names are fractions of a whole note, so the maths is built right in.
British names are older words that describe the note's character, and "quaver" comes from a word
meaning to tremble. Neither is more correct. They are simply two labels for exactly the same sound.
Memory hook: if the name is a fraction, it's American. If it sounds like it belongs in a
Jane Austen novel, it's British.
Notes
Beat values shown in 4/4 time
Semibreve
American Whole note
4 beats
Minim
American Half note
2 beats
Crotchet
American Quarter note
1 beat
Quaver
American Eighth note
1/2 beat
Semiquaver
American Sixteenth note
1/4 beat
Demisemiquaver
American Thirty-second note
1/8 beat
Rests
Silence follows the same pattern, so a quaver rest and an eighth rest are the same thing too