| Element |
A single bar or a single space in a barcode is called an Element. |
| Module |
Modules are used to measure the amount a space used by a bar or a space. The smallest bar in a barcode usually takes up one module. A bar twice as wide takes up two modules. |
| Character |
A character is defined by a specific pattern of bars and spaces. In some barcodes, every character is made up of a set number of modules. |
| Density |
The number of characters than can be encoded per inch in a barcode, after deciding the width of the smallest bar. |
| b |
Maximum allowable error in the printed width of a bar from the correct module width. |
| e |
Maximum allowable error in distance from the beginning of one bar or space to the beginning of the next bar or space. |
| N |
The ratio of the width of the average wide element to that of the average narrow element. |
| p |
The tolerance for error in distance from the beginning of one character to the beginning of the next. (Continuous symbologies only.) |
| t |
The tolerance for error in widths of single characters. |
| X |
The ideal module width. This is often measured in mils, of 1/1000 of an inch. |