a.c.
before meals
gtt or gt
drops
h.s.
at bedtime
o.d.
right eye
a.d.
right ear
o.s.
left eye
a.s.
left ear
o.u.
each eye/both eyes
a.u.
each ear/both ears
ss
one-half (1/2)
p.c.
after meals
prn
as needed
qid
four times daily
q.s. ad
quantity sufficient to make