a tempo
return to the original tempo
accent
a stressed note
accelerando
accelerate; gradually faster
adagio
slowly
allegro
fast or quick, cheerfully, merrily
allegretto
slightly slower than allegro; faster than andante
andante
a moderate walking tempo
andantino
slightly faster than andante, some composers use it to mean slower than andante
animato
animated; with spirit

appoggiatura
used mainly in music of the Classical Period
arpeggio
a broken chord
articulation
the various ways notes are executed (e.g. staccato, legato)
cantabile
in a singing style
con
with
con brio
with vigor, spirit, or brilliance
con moto
with motion
crescendo
gradually louder
D.C. al fine
go back to the beginning of the piece, and play until the word fine
damper pedal
press the pedal on the right
dolce
sweetly
enharmonic
two different names for the same pitch, such as E flat and D sharp
forte
loud
fortissimo
very loud
fortississimo
very, very loud
fermata
hold the note for more than its value
largo
very slowly
legato
smoothly
leggiero
lightly, delicately
lento
slowly
mezzo forte
medium loud
mezzo piano
medium soft
moderato
a moderate or medium tempo
molto
much
mordent

octave sign (8va)
play the note an octave higher
ostinato
a repeated note or figure
parallel Major and minor
Major and minor keys with the same letter names (e.g. A Major and a minor)
piano
soft
pianissimo
very soft
pianississimo
very, very soft
phrase
a musical sentence often lasting around four measures
poco
little
presto
very fast
rallentando (rall.)
gradually slower
ritardando (ritard., rit.)
slow down gradually
sforzando (sF, SFz, Fz)
a sudden, sharp accent
slur
curved line indicating to play legato
spiritoso
spirited; with spirit
staccato
crisp or detached
subito
suddenly
tempo
the speed at which to play music
tenuto
hold the note for its full value, can also mean to stress it
tranquillo
tranquilly, peacefully
tre corde (t.c.)
release the una corda pedal (left pedal)
trill
Baroque / Classical period: performed beginning on the note above the written note
Romantic period: performed beginning on the written note
turn

una corda (u.c.)
press the left (soft) pedal
vivace
quick, lively
vivo
brisk, lively
- etto / - ino
suffixes meaning little