n :  a disaccharide sugar C₁₂H₂₂O₁₁ that is present in milk, yields glucose and galactose upon hydrolysis, yields esp. lactic acid upon fermentation, and is used chiefly in foods, medicines, and culture media (as for the manufacture of penicillin) - called also milk sugar  .
 
   
 
Similar sounding terms:  lac·tase 
 
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