'电话线' (diànhuà xiàn) literally means 'electric-speech-line' — combining 电 (diàn, 'electricity'), 话 (huà, 'speech' or 'talk'), and 线 (xiàn, 'line' or 'wire'). It refers specifically to the physical copper or fiber-optic cable that transmits voice signals for traditional landline telephone service. Unlike wireless communication, this term emphasizes the tangible infrastructure connecting phones to the network.

This word is commonly used in technical, residential, and maintenance contexts — for example, when discussing home wiring, internet installation (since many broadband services use the same lines), or troubleshooting call failures. While increasingly less central with the rise of mobile and VoIP technology, 电话线 remains essential in many rural areas and older buildings. It's a concrete, countable noun and usually appears with measure words like '根' (gēn) — e.g., 一根电话线 — or in plural form without a classifier in general statements.