Glossary of Terms

This glossary of terms is meant to help everyone understand medical words. It is a place to quickly find information on medical words.

To find a word or term begin by clicking on a letter in the A-Z list. Then you can browse down the list to find the word you want. You can also type your medical word in the search box in the upper right corner and then click on the little magnifying glass.

This glossary is for information only. It should never be used instead of advice from a healthcare provider.

If you have questions or comments about the Glossary of Terms please let us know.

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disease-fighting cell


an area at the centre of your eye

magnetic resonance imaging (MRI)

MRI uses magnets, radio waves, and a computer to take pictures of areas inside your body.

imaging of body regions in a variety of different planes using magnetic fields and radio-frequency pulses/radio waves.


size, how serious



severe and become worse, as in malignant hypertension

malignant tumour

cancer, mass


not eating enough food or not eating enough of the foods your body needs


an x-ray of your breast to check cancer


take care of


lower jaw






a lump in the body

how much matter there is in something. Matter is anything you can touch physically


operation to remove your breast

mastoid (mastoid bone)

a large, bony area on the base of the skull behind your ear, it connects with your middle ear


an infection of the mastoid bone in your skull.

the mastoid is found just behind your ear. This infection is most often caused by a middle ear infection


upper jaw


a blotchy, red rash that starts on your head and moves down your body. Measles is caused by a virus


a baby's first feces or bowel movement, poop

A greenish-brown substance that comes from a baby's digestive tract and is ordinarily passed after delivery as the baby's first stool. Sometimes, the meconium is passed before birth, in which case it stains the amniotic fluid, turning it greenish brown.

med rec (Medication Reconciliation)

creating the most accurate list possible of all the medications you are taking, and comparing that list to your admission, transfer, and/or discharge orders

formal process in which health care providers work together with patients and families to ensure accurate medication information is communicated across transitions of care. For further information go to the Institute for Safe Medication Practices Canada website 

medical directive

an indirect doctors order

an order for a procedure or series of procedures that may be implemented for a patient when specific conditions are met and specific circumstances exist. 

medical radiation technologist (MRT)

medical staff who do diagnostic imaging tests (such as x-rays and scans) and give radiation therapy treatments

current description of any medical radiation worker in Ontario licensed under the College of Medical Radiation Technologists of Ontario; encompasses all disciplines of medical radiation work including x-ray technologists, nuclear medicine technologists, radiation therapy technologists, and magnetic resonance imaging (MRI) technologists.


drug, pill, medicine


skin cancer


black, thick stool (bowel movement) that has blood in it


a very thin layer of tissue that covers a surface

the sac that surrounds the baby in the uterus and contains amniotic fluid in which the baby floats. Also called the bag of waters or amniotic sac, the membranes will rupture naturally or be ruptured artificially during labour


a rubbery piece of cartilage that acts as a shock absorber for your knee


time in a woman's life when her period stops, also called the "change of life"


woman's period

periodic blood that flows as a discharge from the uterus

mental health condition

mental illness

illness that affects your mood, thinking and behaviour


frame of mind, outlook


how your body uses food to make energy

metastasis (metastatic)

when cancer grows and spreads to other parts of your body

methicillin resistant staphylococcus aureus (MRSA)

bacteria, bacteria that is hard to kill with antibiotics

bacteria that is spread by skin-to-skin contact or through contact with items contaminated by the bacteria

bacteria that causes infections in different parts of the body. It is harder to treat than normal Staphylococcus Aureus because it is resistant to many common antibiotics, including methicillin, penicillin, amoxicillin, and cephalosporins.


germs, bacteria

tiny germs that are too small to see


a person who is trained to help with child birth 


move, travel


gentle, slight, small




least, small, smallest


make smaller, lessen, decrease


to lose a baby


make less harmful, lessen, reduce

mitral valve

a valve in your heart

a 2-part valve in the left side of your heart that controls blood flow between the top (atrium) and the bottom (ventricle)

MMR vaccine (measles, mumps and rubella vaccine)

a shot that helps prevent measles, mumps, and rubella


being able to move

walking, standing up, moving from one chair to another


medium, mild

neutral, middle-of-the road




back teeth

mold (mould)


form, pattern, impression


 sickness or illness



mortality rate

number of deaths

motor neuron

a nerve cell that sends messages from your central nervous system to your muscles

motor neuron disease

when special nerve cells in your brain and spinal cord called motor neurons stop working properly


phlegm, nose fluid, mouth fluid, throat coating

fluid present in the nose and windpipe

a thick fluid produced by the lining of some tissues of the body

multiple myeloma

cancer of your white blood cells 

multiple sclerosis (MS)

disease of your nerves

chronic autoimmune disorder affecting movement, sensation, and bodily functions. It is caused by destruction of the myelin insulation covering nerve fibers (neurons) in the central nervous system (brain and spinal cord).


an illness that causes swelling of the glands that make your saliva 

muscle atrophy

when your muscles get smaller and weaker

muscle contraction

muscle movement


something that causes change


change over time

myasthenia gravis

a disease that causes weakness in your muscles and makes it hard to control them

mycophenolate mofetil

medication that is used to prevent rejection of your new kidney after you have a kidney transplant


a white tissue forming a cover around certain nerve fibres


disease of your spinal cord

a condition where there is a loss of neurological function related to your spinal cord


myocardial infarction (MI)

heart attack


it's easy for you to see things close up, but harder to see things that far away