| Abbreviation | Definition |
|---|---|
| NT | Newton |
| NTU | Nephelometric Turbidity Unit |
| NU | Normalized Units |
| NW | North West |
| NY | Native Yard |
| NYM | New York Minute |
| O | pint |
| O.D. | Outside Diameter |
| OAR | Of A Revolution |
| obl. | oblong |
| OBQ | On Board Quantity |
| OCI | One Chance In |
| OD | Outside Dimensions |
| ODI | Optimum Daily Intake |
| OGP | Open Gap Platen |
| OH | Office Hour |
| OM | One Million |
| OPSY | Ounces Per Square Yard |
| OZ | Ounce |
| oz. | ounce |