Webster's New World Medical Dictionary

preop
Short for preoperative; before a surgical
operation. The opposite of preop is postop.
prepuce
See 
foreskin.
prepuce, inflammation of the
See 
posthitis.
presbyopia
The loss of the eye’s ability to change
focus to see near objects due to advancing age.
Presbyopia is said to be due to the lens becoming
less elastic with age. The first sign of presbyopia is
often the need to hold reading material farther away.
See 
eye.
prescription
A physician’s order for the prepa-
ration and administration of a drug or device for a
patient. A prescription has several parts, including
the superscription, or heading, with the symbol R or
Rx, which stands for the word “recipe” (Latin for
“to take”); the inscription, which contains the
names and quantities of the ingredients; the sub-
scription, or directions for compounding the drug;
and the signature, often preceded by the sign s.,
which stands for “signa” (Latin for “mark”), giving
the directions to be marked on the container. See
also Appendix A, “Prescription Abbreviations.”
prescription drug
A drug requiring a prescrip-
tion, as opposed to an over-the-counter (OTC)
drug, which can be purchased without a prescrip-
tion. See also 
prescription.
presentation, breech
See 
breech birth.
presentation, footling
See 
footling birth.
presentation, vertex
See 
vertex birth.
pressure, high blood
See 
hypertension.
pressure, intraocular
See 
intraocular pressure.
pressure, low blood
See 
hypotension.
prevalence
The proportion of individuals in a
population having a disease or characteristic.
Prevalence is a statistical concept referring to the
number of cases of a disease that are present in a