China 
Africa 
- Inner nuclear layer
- Inner plexiform layer
- Inner root sheath
- Innervation
- Inoculation
- Inoculation needle
- Inoculum
- Inonotus obliquus
- Inorganic acids
- Inorganic carbon
- Inorganic chemicals
- Inorganic chemistry
- Inorganic compounds
- Inorganic phosphate
- Inorganic pyrophosphatase
- Inosine
- Inosine-5′-monophosphate dehydrogenase
- Inosinic acid
- Inositol
- Inositol 1 4 5 trisphosphate
- Inositol phosphate
- Inositol polyphosphate-5-phosphatase
- Inositol trisphosphate
- Inositol trisphosphate receptor
- Inositol-polyphosphate 5-phosphatase
- Inotersen
- Inotropes
- Inotropic
- Inotuzumab ozogamicin
- Inovirus
- Inquest
- Insanity
- Insanity defense
- Insect bite
- Insect repellent
- Insect vector
- Insecticides
- Insemination
- Insertion sequences
- Insertional mutagenesis
- Insight-oriented psychotherapy
- Insomnia
- Inspiratory reserve volume
- Instantaneous wave-free ratio
- Institute for Quality and Efficiency in Health Care
- Institutional Animal Care and Use Committee
- Institutionalization
- Instructional design
- Instrument myopia
- Instrumental conditioning
- Instrumentation
- Insufflation
- Insula
- Insular cortex
- Insulators
- Insulin analog
- Insulin aspart
- Insulin degludec
- Insulin dependent diabetes mellitus
- Insulin detemir
- Insulin glargine
- Insulin glulisine
- Insulin index
- Insulin lispro
- Insulin pump
- Insulin receptor
- Insulin receptor substrate
- Insulin resistance
- Insulin response
- Insulin secretion
- Insulin sensitivity
- Insulin shock
- Insulin signaling
- Insulin-degrading enzyme
- Insulin-like growth factor
- Insulin-like growth factor 1
- Insulin-like growth factor 1 receptor
- Insulin-like growth factor 2
- Insulin-like growth factor I
- Insulin-like growth factor receptor
- Insulin-like growth factor-binding protein
- Insulinoma
- Insulitis
- Insults
- Integral membrane proteins
- Integrase
- Integrase inhibitors
- Integrated Management of Childhood Illness
- Integrated care
- Integrated pest management
- Integrated stress response
- Integrative medicine
- Integrin alpha V
- Integrin receptor
- Integrins
- Integrity
- Integrons
- Integument
- Integumentary system
- Inteins
- Intelectin
- Intellectual and developmental disabilities
- Intellectual disability
- Intellectual impairment
- Intellectualization
- Intelligence
- Intelligence assessment
- Intelligence tests
- Intelligibility
- Intensity
- Intensive Interaction
- Intensive insulin therapy
- Intensive outpatient programs
- Intention
- Intention to treat analysis
- Intention tremor
- Inter-alpha-trypsin inhibitor
- InterPro
- Interactions
- Interactome
- Interatrial septum
- Intercalated discs
- Intercalated duct
- Intercarpal joint
- Intercavernous sinus
- Intercavernous sinuses
- Intercellular adhesion molecule 1
- Intercellular cleft
- Intercellular communication
- Intercellular junctions
- Interclavicular ligament
- Intercondylar fossa
- Intercostal arteries
- Intercostal muscle
- Intercostal muscles
- Intercostal nerve
- Intercostal nerve blocks
- Intercostal spaces
- Intercostal veins
- Intercostobrachial nerve
- Interdigitating dendritic cell sarcoma
- Interfacial polymerization
- Interference competition
- Interference microscopy
- Interference theory
- Interferogram
- Interferometers
- Interferometry
- Interferon
- Interferon alfa