The term 'cellular ___' can be completed with the word 'ONE' (3 letters) and 'PHONE' (5 letters). Cellular ONE and cellular PHONE are terms used to describe mobile phones that use cellular networks to connect to the internet. Cellular networks are wireless networks that use radio waves to transmit data between cell towers and mobile devices. Cellular phones are a type of mobile device that allow users to make calls, send text messages, access the internet, and more.