Africa 
China 
Japan 
MENA 
- Marchiafava-Bignami disease
- Marek's disease
- Maresin
- Marfan syndrome
- Marfanoid
- Margaric acid
- Margatoxin
- Margin of error
- Marginal Structural Model
- Marginal distribution
- Marginal mandibular branch
- Marginal sinus
- Marginal zone
- Marginal zone B cells
- Marginal zone B-cell lymphoma
- Marginal zone lymphoma
- Marginalization
- Maribavir
- Marijuana abuse
- Marimastat
- Marine pollution
- Marine snow
- Marinobacter
- Marionette lines
- Marjolin's ulcer
- Marjoram
- Marker chromosome
- Marker gene
- Marker-assisted selection
- Marketing authorisation
- Marlex
- Marlowe-Crowne Social Desirability Scale
- Marmesin
- Maroteaux-Lamy syndrome
- Marrow adipose tissue
- Marsh gas
- Marshall syndrome
- Marsupialization
- Martin-Gruber Anastomosis
- MasSpec Pen
- Masked depression
- Masked hypertension
- Masking
- Masking agent
- Maslach Burnout Inventory
- Maslinic acid
- Maslow's hierarchy of needs
- Masochism
- Maspin
- Mass attenuation coefficient
- Mass balance
- Mass casualty incidents
- Mass communication
- Mass concentration
- Mass cytometry
- Mass density
- Mass diffusivity
- Mass hysteria
- Mass spectrometer
- Mass spectrometry
- Mass spectroscopy
- Mass spectrum
- Mass vaccination
- Massage therapy
- Masseter muscle
- Massive perivillous fibrin deposition
- Masson's trichrome stain
- Mast cell
- Mast cell activation syndrome
- Mast cell leukemia
- Mast cell sarcoma
- Mast cell stabilizers
- Mast cell tumors
- Mast-cell sarcoma
- Mastadenovirus
- Mastalgia
- Mastectomy
- Mastic
- Mastication
- Mastitis
- Mastocytoma
- Mastocytosis
- Mastoid
- Mastoid antrum
- Mastoid process
- Mastoidectomy
- Mastoiditis
- Mastoparan
- Mastopexy
- Mastrevirus
- Matairesinol
- Matchbox sign
- Matching
- Matching law
- Mate
- Materia medica
- Material safety data sheet
- Maternal deprivation
- Maternal effect
- Maternal inheritance
- Maternal morbidity
- Maternal mortality
- Maternal mortality ratio
- Maternal near miss
- Maternal recognition of pregnancy
- Maternal to zygotic transition
- Maternal-fetal medicine
- Maternity hospital
- Maternity ward
- Mathematical expectation
- Mathematical model
- Mating type
- Mating-type locus
- Matricaria chamomilla
- Matricaria recutita
- Matricellular proteins
- Matrigel
- Matrilin
- Matrine
- Matriptase
- Matrix
- Matrix Gla protein
- Matrix gla protein
- Matrix metalloproteinase
- Matrix metalloproteinase inhibitor
- Matrix protein
- Matrix-M
- Maturation inhibitor
- Maturation promoting factor
- Mature minor doctrine
- Mature teratoma
- Maturity
- Maturity onset diabetes of the young
- Maturity-onset diabetes of the young
- Matuzumab
- Mavrilimumab
- Maxillary
- Maxillary antrum
- Maxillary artery
- Maxillary first molar
- Maxillary hypoplasia
- Maxillary nerve
- Maxillary prominence
- Maxillary second molar
- Maxillary second premolar
- Maxillary sinus
- Maxillary tuberosity
- Maxillary vein
- Maxillofacial surgery
- Maxillomandibular advancement