| CFL | Compact fluorescent lamp |
| COO | Chief Operating Officer |
| COVID-19 | COrona VIrus Disease 2019 |
| CBI | Central bureau of Investigation |
| CBI | Central Bank of India |
| CDMA | Code Division Multiple Access |
| CAIIB | Certified Associate of Indian Institute of Bankers |
| CAT | Common Admission Test |
| CPT | Common Proficiency Test |
| CV | Curriculum Vitae |
| CGPA | Cumulative Grade Point Average |
| CAD | Computer Aided Design |
| CCTV | Closed Circuit Television |
| CRT | Cathode Ray Tube |
| CA | Chartered Accountant |
| CAG | Comptroller and Auditor General of India |
| COB | Close of Business |
| CRR | Cash Reserve Ratio |
| CST | Central Sales Tax |
| CST | Chhatrapati Shivaji Terminus |
| CST | Central Standard Time |
| CTS | Cheque Truncation System |
| CTS | Clear to Send |
| CTS | Certified Technology Specialist |
| CTS | Cognizant Technology Solutions |
| COMPUTER | Computer |
| CPU | Central Processing Unit |
| CNG | Compressed Natural Gas |
| CABG | Coronary Artery Bypass Graft |
| CBC | Complete Blood Count |
| CHF | Congestive Heart Failure |
| CMO | Chief Medical Officer |
| COPD | Chronic Obstructive Pulmonary Disease |
| CPR | Cardio-Pulmonary Resuscitation |
| CC | Cubic Capacity / Cubic Centimeter |
| CC | Carbon Copy |
| CC and BCC | Carbon Copy and Blind Carbon Copy |
| CNG | Compressed Natural Gas |
| CBSE | Central Board of Secondary Education |
| CEO | Chief Executive Officer |
| CID | Crime Investigation Department |
| CISF | Central Industrial Security Force |
| CRISIL | Credit Rating Information Services of India Limited |
| CRPF | Central Reserve Police Force |
| CNC | Computerized Numerical Control |
| CGI | Computer-Generated Imagery |
| CLAT | Common Law Admission Test |
| CSC | Civil Service Commission |
| CCC | Civilian Conservation Corps |
| CFO | Chief Financial Officer |
| CTC | Cost to Company |
| CMS | Content management system |
| CMS | Centers for Medicare and Medicaid Services |
| CE | Common Era |
| C&P | Copy and Paste |
| CU | See you |
| CYS | Check your Settings |
| CFT | Combating the Financing of Terrorism |
| CRM | Customer Relationship Management |
| CSS | Cascading Style Sheet |
| COBOL | Common Business Oriented Language |
| CTET | Central Teacher Eligibility Test |
| CABG | Coronary Artery Bypass Grafting |
| CT | Chemotherapy |
| CVA | Cerebrovascular Accident |
| CAST Time Zone | Casey Time (Standard Time) |
| CAT Time Zone | Central Africa Time (Standard Time) |
| CCT Time Zone | Cocos Islands Time (Standard Time) |
| CDT Time Zone | Central Daylight Time / Central Daylight Saving Time (Daylight Saving Time) |
| CEST Time Zone | Central European Summer Time (Daylight Saving Time) |
| CET Time Zone | Central European Time / European Central Time (Standard Time) |
| CHADT Time Zone | Chatham Island Daylight Time (Daylight Saving Time) |
| CHAST Time Zone | Chatham Island Standard Time (Standard Time) |
| CHOST Time Zone | Choibalsan Summer Time (Daylight Saving Time) |
| CHOT Time Zone | Choibalsan Time (Standard Time) |
| CHUT Time Zone | Chuuk Time (Standard Time) |
| CIDST Time Zone | Cayman Islands Daylight Saving Time (Daylight Saving Time) |
| CIST Time Zone | Cayman Islands Standard Time (Standard Time) |
| CKT Time Zone | Cook Island Time (Standard Time) |
| CLST Time Zone | Chile Summer Time (Daylight Saving Time) |
| CLT Time Zone | Chile Standard Time (Standard Time) |
| COT Time Zone | Colombia Time (Standard Time) |
| CST Time Zone | Central Standard Time / Central Time (Standard Time) |
| CT Time Zone | Central Time |
| CVT Time Zone | Cape Verde Time (Standard Time) |
| CXT Time Zone | Christmas Island Time (Standard Time) |
| CLI | Command Line Interface |
