communications

Only the countable uses of communication take this plural: separate messages, exchanges or conversations, and also passages or openings that connect two places. The uncountable idea of exchanging information has no plural, so communications here points to particular items, such as letters, emails or calls. The same spelling also names the field of telecommunications, which exists only in the plural.

A field name that never sheds its -s: there is no singular for this sense, and the plural stays even when the word modifies another noun. Simon Jenkins, writing in 2012, mocks David Cameron's communications data bill, not a communication data bill. Telecommunications is the fuller name for the same field. Communications is the everyday short form, especially in compounds like communications satellite or communications network.

Here the word names a job and a department rather than a technology. A communications director handles press releases and staff memos, not cables or signals. Like the telecommunications field, it keeps its plural form, and that plural separates the department from the general activity of organizational communication. Only context tells these two plural-only senses apart, so a phrase like communications budget can point either way.