The term "width" can be interpreted in different ways when referring to a QSFP (Quad Small Form-factor Pluggable) module. In the context of QSFP, it usually refers to the physical dimensions of the module.

The dimensions of a QSFP module are standardized, and the width is typically measured in millimeters. The QSFP module has a width of approximately 18.35 mm (0.722 inches). This measurement is based on the width across the front face of the transceiver module.

Keep in mind that the term "width" might also be used in the context of the electrical interface, where it could refer to the number of electrical lanes or channels. A QSFP module commonly supports four independent channels, each operating at a specific data rate (e.g., 10 Gbps, 25 Gbps, 40 Gbps, or 100 Gbps). Therefore, it can be described as a "quad" form-factor, reflecting its support for four channels.

In summary, the physical width of a QSFP module is around 18.35 mm, and it supports four channels for data transmission.