Definition of side effect in US English:

side effect


  • A secondary, typically undesirable effect of a drug or medical treatment.

    ‘many anticancer drugs now in use have toxic side effects’
    • ‘Researchers may have found a side effect associated with stress which could lead to premature aging.’
    • ‘She thinks the only lasting side effect from the treatment may be some memory loss.’
    • ‘A side effect of many of these drugs is sedation, so it's better to take them before going to sleep at night.’
    • ‘Alcohol has a side effect and may impact your ability to do what you need to do when you need to do it, even the next day.’
    • ‘She went deaf when she was a baby, before the age of the cochlear implant, as a side effect of polio.’
    • ‘Diarrhea is a common side effect of tube feedings in the intensive care unit.’
    • ‘If the radiation is aimed at your abdominal or pelvic area, diarrhea may be a side effect.’
    • ‘Most of those who had had a stroke were aware of their own drug treatment and were concerned about the side effect of drugs.’
    • ‘Cough, a side effect not related to dose, was severe enough to prohibit further use in only three patients.’
    • ‘The most common side effect of the influenza vaccine is soreness at the vaccination site.’
    • ‘Blurred vision is a common side effect, but it usually goes away on its own within a couple of weeks.’
    • ‘Tiredness is a side effect that can be experienced by anyone undergoing radiation.’
    • ‘Tell your doctor if you have had a particular side effect from a pain medication in the past.’
    • ‘Cough was the only side effect that was more prevalent in this group than in the placebo group.’
    • ‘Some people are able to use a different kind of statin without the same side effect.’
    • ‘Be sure to tell your doctor about any changes in your body that might be a side effect from the medicine.’
    • ‘Scarring can also be a side effect or complication of other conditions.’
    • ‘But the side effect intrigued him into the exact workings of the hormone.’
    • ‘My dad has to take Provigil to counteract the drowsiness side effect of his other medication.’
    • ‘If priapism has occurred as a side effect of medication then a different medication can usually be prescribed.’
    consequence, entailment, corollary, concomitant
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side effect

/ˈsīd əˌfekt//ˈsaɪd əˌfɛkt/