o (objective)

O (oxygen [element])

O (oral)

O (other)

O (ovulation)

O-A (occipital-atlas)

O.D. (right eye (L. oculus dexter))

o.h. (every hour (L. omni hora))

o.m. (every morning (L. omni mane))

o.n. (every night (L. omni nocte))