Environmental Studies
- initial strontium ratio
- innate
- inselberg
- insight learning
- instability
- intensity scale
- intention movement
- inter-
- interception
- interflow
- interglacial
- Interglacial periods
- intermediate rock
- intermittent stream
- International Biological Programme
- International Code of Botanical Nomenclature
- International Cooperation
- interstade
- interstadial
- interstitial