| Abbreviation | Definition |
|---|---|
| Ir | Iridium |
| IRAA | Internal Reference Amino Acid |
| IRM | Interference Reflection Microscopy |
| IRS | indoor residual spray |
| ISA | Instrumentation Systems and Automation |
| ISBR | Interchange Sequencing Batch Reactor |
| ISBZ | IsoStearyl BenZoate |
| ISC | Iron Sulfur Cluster |
| ISCB | Indian Society of Chemists and Biologists |
| ISCO | Index for Selective Carbon Oxidation |
| ISCR | In Situ Chemical Reduction |
| ISI | Initial State Interaction |
| ISI | In-Situ Interferometer |
| ISOCS | International Society on Olfaction and Chemical Sensing |
| ISOCS | International Symposium on Organic Chemistry of Sulfur |
| ISP | Isolated Soy Protein |
| ISPC | International Society for the Philosophy of Chemistry |
| ITCT | Intercontinental Transport and Chemical Transformation |
| ITE | Incompatible Trace Element |
| ITO | indium-tin-oxide |