| Acronym | Meaning |
| CHIEF | Clearinghouse For Inventories And Emission Factors |
| CHIGFET | Complementary Heterostructure Insulated Gate Field Effect Transistor |
| CHIME | (chem. Th-U-total Pb Isochron Method) |
| CHIP | Chemical Hazard Information Profile(s) |
| CHIP | Cold And Hot Isostatic Pressing |
| CHIRP | Core-hole Initiated Relaxation Process (in Ionic Crystals) |
| CHM | Complete Hydatidiform Mole |
| CHMM | Certified Hazardous Materials Manager |
| CHMO | Constrained Hartree-Fock Orbitals |
| CHMOS | Complementary High-performance Metal-oxide Semiconductor |
| CHO | Chinese Hamster Ovary |
| CHO | Complex Harmonic Oscillator (in Mol. Scattering Theory) |
| CHORTLE | Carbon-hydrogen Correlation From One-dimensional Polarization-transfer Spectra By Least-squares Analysis |
| CHORUS | CERN Hybrid Oscillation Research Apparatus |
| CHP | Chemical Hygiene Plan |
| CHP | Combined Heat Power |
| CHQ | Cold Heading Quality |
| CHR | Conventional Hot Rolling |
| CHRIS | Chemical Hazards Response Info System |
| CHRM | Characteristic Remanent Magnetization |
| CHT | Continuous Heating Transformation [curing Diagram] |
| CHTS | Combinatorial High-throughput Screening |
| CHW | Coherent Hole Wave (quantum Excitations In Solids) |
| CHWMP | County Hazardous Waste Management Plan |
| CI | Chemical Ionization |
| CI | Compression-ignition (engine) |
| CI | Configuration Interaction |
| CI-HY | Configuration Interaction-Hylleraas |
| CI-TD-HG | Configuration Interaction Time-dependent Hartree Grid |
| CIA | Chemical Industries Association |
| CIA | Capillary Ion Analysis |
| CIAC | Centro De Informacion Ambiental Del Caribe |
| CIAP | Climatic Implications Of Atmospheric Pollution |
| CIAP | Climate Impact Assessment Program |
| CIAQ | Canadian Indoor Air Quality |
| CIAQ | Council On Indoor Air Quality |
| CIBE | Continuous Interfacial Bilayer Electrode |
| CIBL | Convective Internal Boundary Layer |
| CIBO | Council Of Industrial Boiler Owners |
| CIBS | Corrections To An Incomplete Basis Set (a Perturbation Theory) |
| CIC | Consumer Information Catalog |
| CIC | Configuration Interaction (in The) Continuum (theory In Calcns. Of Atomic Resonances) |
| CICAD | Concise International Chemical Assessment Documents |
| CICIS | Chemicals In Commerce Information System |
| CID | Charge Injection Device |
| CID | Collision-induced Dissociation |
| CID | Configuration Interaction With Double Substitution |
| CID | Configuration Interaction With Doubly Excited Configurations |
| CIDA | Cometary Impact Dust Analyzer |
| CIDEP | Chemically Induced Dynamic Electron Polarization |