Here are some common meanings of medical prefixes:

• A- or An- (G) from, without: asepsis, without infection.
• A- or Ab- (L) away, lack of: abnormal, departing from normal.
• Ad- (L) to, toward, near: adrenal, near the kidney.
• Ambi- (L) both: ambidextrous, referring to both hands.
• Ante- (L) before: antenatal, occurring or having been formed before birth. Anti- (G) against: antiseptic, against or preventing sepsis.
• Auto- (G) self: auto-intoxication, poisoning by toxin generated in the body.
• Bi- or Bin- (L) two: binocular, pertaining to both eyes.
• Brady- (G) slow: bradycardia, abnormal slowness of heartbeat.
• Circum- (L) around: circumocular, around the eyes.
• Contra- (L) against, opposed: contraindication, indication opposing usually indicated treatment.
• Counter- (L) against: counterirritation, an irritation to relieve some other irritation (e.g., a liniment) .
• Di- (L) two: diphasic, occurring in two stages or phases.
• Dis- (L) apart: disarticulation, taking joint apart.
• Dys- (G) pain or difficulty: dyspepsia; impairment of digestion.
• Ecto- (G) outside: ectoretina, outermost layer of retina.
• Em- or En- (G) in: encapsulated, inclosed in a capsule.
• End- (G) within: endothelium, layer of cells lining heart, blood and lymph vessels.
• Epi- (G) above or upon: epidermis, outermost layer of skin.
• Erythro- (G) red: erythrocyte, red blood cell.
• Eu- (G) well: euphoria, well feeling, feeling of good health.
• Ex- or E- (L) out: excretion, material thrown out of the body or the organ.
• Exo- (G) outside: exocrine, excreting outwardly (opposite of endocrine) .
• Extra- (G) outside: extramural, situated or occurring outside a wall.