On Monday, 12 January 2026, between 07:00 and 10:00 CET (Amsterdam time), this website will be unavailable due to scheduled maintenance.
This resource focuses on side effects and other terms used in medicines information and assessments of medicines. It does not include terms that are used only rarely, nor does it cover most disease states or technical terms.
How to use EMA’s medical terms simplifier
- You can search for a term or click on a letter below to see terms beginning with that letter.
- Each entry contains a short description. For some, a longer or alternative description is available by selecting the term.
- We use ‘< >’ to indicate alternative or optional wording.
EMA’s medical terms simplifier will be updated periodically. For comments or suggestions, you can use our Medical terms simplifier comments form.
I
-
Icterus
see jaundice -
Idiopathic
the cause of the disease is unknown -
Idiopathic thrombocytopenic purpura (ITP)
a disease in which people do not have enough platelets and are at high risk of bleeding -
Ileum (ileal)
last part of the small intestine -
Ileus
loss of movement in bowel muscles -
Immediate-release tablet
a tablet that releases the active substance immediately -
Immune reactivation syndrome
see immune reconstitution syndrome -
Immune reconstitution inflammatory syndrome (IRIS)
see immune reconstitution syndrome -
Immune reconstitution syndrome
when the recovering immune system starts fighting off hidden infection, causing inflammation and damage to healthy tissue <such as the liver and thyroid gland> -
Immune system
the body's natural defences -
Immunity
protection -
Immunocompetent person
person with an immune system that works normally -
Immunocompromised person
person with a weakened immune system -
Immunodeficiency disorder, primary
when body defences are reduced from birth -
Immunogenicity
the ability to make the immune system respond to the <viruses/bacteria etc.>; [in studies] the ability of X to trigger the production of antibodies -
Immunoglobulins
antibodies; see antibody -
Immunological response
triggering of the body’s defences against <an organism or a foreign substance> -
Immunomodulator
a substance that changes the activity of the body’s defences -
Immunosuppressant medicine
a medicine that reduces the activity of the immune system -
Immunosuppressive
reduces the activity of the immune system -
Immunotherapy
medicines that stimulate the immune system <to kill the cancer cells> -
Impetigo
a skin infection causing crusting scabs -
Inactivated (vaccine)
see vaccine, inactivated -
Incidence
the number of people who get the <disease/condition/illness> every <year> -
Incontinence
lack of control over passing <urine><stools> -
Incontinence, stress
accidental leaks of urine caused by sudden pressure on the bladder <brought on, for example, by coughing, laughing, lifting and exercising> -
Incontinence, urge
see urinary urgency -
Indolent
slow-growing (cancer) -
Induration
hardening <at the injection site> -
Indwelling intravenous cannula
see cannula, indwelling intravenous -
Infection, complicated
infection that is difficult to treat because it has spread within the body or because the patient has other conditions -
Infection, upper respiratory tract
nose and throat infection -
Infection, urinary tract
Infection of the parts of the body that collect and pass out urine -
Influenza
flu -
Infusion
drip -
Insomnia
difficulty sleeping -
Insomnia, primary
insomnia with no identified cause <including medical, mental or environmental causes> -
Interstitial lung disease
see lung disease, interstitial -
Intra-abdominal infections
infections within the abdomen (belly) -
Intracranial
within the skull <in or around the brain> -
Intradermal
<within><into> the skin -
Intramuscular
into a muscle -
Intraocular
into the eye -
Intraspinal analgesia
analgesic, intraspinal -
Intrathecal
into the spinal canal <into the fluid surrounding the spinal cord> -
Intravenous<ly>
into a vein -
Intravitreal
inserted into the vitreous humour, the jelly-like fluid in the eye -
Intubation
insertion of a breathing tube through the nose or the mouth -
Intussusception
when part of the bowel becomes enfolded within another part of the bowel, leading to a blockage -
Invasive disease
disease <that has spread> <capable of spreading> to other parts of the body -
Invasive procedure
a medical procedure that may involve piercing or cutting into the body or inserting instruments -
Ions
charged particles -
Iron overload
an excess of iron in the body -
Ischaemia
reduced blood supply -
Ischaemic heart disease
see coronary heart disease -
Ischaemic stroke
see stroke, ischaemic