an essential part of every Bluetooth subsystem, officially abbreviated to HCI

Hypothesis of Collective Imprudence, the term for a sociological phenomenon coined by John Derbyshire in 2006.

Health Communications, Inc., publishers of the Chicken Soup for the Soul series of books

Harmonised Competitiveness Indicators, a measure of euro area countries' price competitiveness used by the ECB.

Advanced HCI (AHCI)

Host Controller Interface

Handgun Control Incorporated, the former name of the Brady Campaign to Prevent Gun Violence, a gun control advocacy group.

Harbord Collegiate Institute and Humberside Collegiate Institute, two schools in Toronto, Canada.

Home Computer Initiative, a UK Government programme designed to increase home computing.

Open HCI (OHCI), Universal HCI (UHCI), Enhanced HCI (EHCI) are USB controllers

Human-Computer Interaction, the study of the interaction between people and computers.

Human-Computer Interface, the technical means by which a human interacts with hardware or software.

Hwa Chong Institution, a school located in Singapore.

HCI is a common typographical error for HCl (with lowercase "L"), see hydrogen chloride and hydrochloric acid.

HCI Capital, a financial enterprise in Hamburg, Germany.