The term internet was originally coined as a shorthand for internetwork in the first specification of the Transmission Control Program, RFC 675, by Vint Cerf, Yogen Dalal, and Carl Sunshine.

The core network became increasingly known as the Internet, treated as a proper noun.

IBM's TCP/IP Tutorial and Technical Overview from 1989 (updated in 1998) stated that the word internet (also internetwork) is simply a contraction of the phrase interconnected network. However, when written with a capital "I", the Internet refers to the worldwide set of interconnected networks.

Another column said that Internet might, like some other commonly used proper nouns, lose its capital letter.

A New York Times column said that Internet has been changing from a proper noun to a generic term.

In their 2009 book Internet Inquiry, academics Annette Markham and Nancy Baym reported that the current tendency within the field of Internet studies has been to use an uncapitalized internet.

The AP Stylebook since 2016 recommends the lowercase form in every case. In 2016, the Oxford English Dictionary found that, based on a study of around 2.5 billion printed and online sources, "Internet" was capitalized in 54% of cases, with Internet being preferred in the United States and internet being preferred in the United Kingdom. Various style manuals, including The Chicago Manual of Style, the Associated Press's AP Stylebook, and the AMA Manual of Style, revised their formerly capitalized stylization of the word to lowercase internet in 2016.