In human-computer interaction, a command verb is a verb

Verb

A verb, from the Latin verbum meaning word, is a word that in syntax conveys an action , or a state of being . In the usual description of English, the basic form, with or without the particle to, is the infinitive...

 that appears in a user interface

User interface

The user interface, in the industrial design field of human–machine interaction, is the space where interaction between humans and machines occurs. The goal of interaction between a human and a machine at the user interface is effective operation and control of the machine, and feedback from the...

 and which is used for the user to tell the computer to do something (rather than vice-versa). For instance, the words "edit" and "view" and "help" which appear in the web browser

Web browser

A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier and may be a web page, image, video, or other piece of content...

 menu are all clearly verbs. Other items such as "file" or "favorites" or "tools" are nouns, but the verb appears in the submenu, for instance, "save", "open", "send", "add to", or "organize".

A web page

Web page

A web page or webpage is a document or information resource that is suitable for the World Wide Web and can be accessed through a web browser and displayed on a monitor or mobile device. This information is usually in HTML or XHTML format, and may provide navigation to other web pages via hypertext...

 typically includes a few such verbs also, typically including "search", "log in" and perhaps "edit this page".

A reflexive user interface is one in which commands and perhaps other controls are defined in the interface itself.