| Word | Description |
| E-commerce | Conducting business activities - buying, selling, and other transactions via the Internet. |
| E-commerce Merchant Account | The type of merchant account necessary to accept credit cards over the Internet. It is a variant of a card-not-present account. See also Merchant Account. |
| ECI | Electronic Commerce Indicator. Use of this field is mandated by the banks and used to determine the source of the original transaction request. |
| Encryption | Encoding and securing information by converting its format for transmission. Receivers of the encrypted message must decrypt it to read it. |