Strictly speaking, a hologram is a recorded interference pattern that reconstructs a light field. Almost nothing marketed as holographic — stage projections, heads-up displays, floating UI in games — meets that definition. And it does not matter, because “holographic interface” has come to name something real: a design language, not a display technology.
That language has three grammatical rules. Depth is meaningful: elements exist at distances, and nearer means more immediate. Light is state: glowing things are interactive, brighter things are active, dimmed things are context. Translucency is honesty: you can see that the interface is layered over a world, and the world remains visible through it.
The language shipped long before the hardware. Game HUDs, automotive dashboards, and spatial-computing headsets all speak it fluently on ordinary screens. Holovate's land console and world HUD are written in it deliberately — translucent panels over live terrain, emissive selection states, depth cues doing hierarchy work that borders and boxes would do in a flat app.
Whether true volumetric displays ever become commonplace, the grammar is already useful: it lets an interface coexist with a world instead of covering it. That is the actual promise hiding inside the word “holographic”.
See the grammar in use in the Holovate frontier.