Weird words of the day

(un) amour (pronounced ah - moor)= love
(un) délice (day - lee - ss) = delight
(un) orgue (org) = an organ (the instrument, not the body part)

These three have an unusual common trait: when singular, they are masculine, but they become feminine when plural. E.g.:
un amour passager = a love that doesn't last
mes premières amours = my first loves