Glossary

Official terminology used in various contexts/by various groups.

Plot Terminology
心面 shinmen: Persona (literally "heart-mask"). Preferred government usage; although the word ペルソナ is inextricable from the experience of having one, foreign words are still avoided where possible.

Shadow (1) (影 kage): A manifestation of the repressed emotions of a particular human within the 異世界/collective unconscious. When accepted and tamed, becomes a Persona.

Shadow (2) (シャドウ shadou): Manifestations of the negative emotions of humanity as a whole; endemic to the 異世界. While they can exist in the real world (see: P3, Port Island experiments), it is extremely difficult to keep them stable, making experimentation difficult and highly dangerous.

? Alternate Worlds (異世界 isekai): Collective terms for the various Realms of Adventure/parallel dimensions in which Personas and Shadows manifest: specifically, the Dark Hour, the TV World, and Utopia. Though a link has been theorized, it has not yet been proven. 外世 (gaiyo, Outside Worlds) is often used in less official conversation.

Gate: An artificial portal to the 異世界, created via the space-time manipulation properties of the Plumes of Dusk. Previously, Shadows had been used for this purpose, but they proved extremely unstable, causing more than one operative to be lost when Gates closed behind them. Because Plumes of Dusk are so rare and useful for so many other purposes, only one or two Gates exist at any given time.

Utopia (理想郷 risoukyou): The world of Reflections. Coined by Kamijo for perhaps obvious reasons, introduced to Chitoku by the mole to try to influence thinking about it. The realm of DIVINE ANTAGONIST, linked to the other 異世界 (that is to say, manifestations of the collective unconscious) but a bounded domain of its own. Shadows are not native to Utopia--after all, a world with no egos has nothing that can give birth to them--but it has similar constructs (see Shards), and there is some bleed from the other 異世界, some intentional (DIVINE ANTAGONIST using them as tools) and some not (influence from the protagonists).

? Shards (鏡片 kyouhen): The Utopia equivalent of Shadow (2): servitors of DIVINE ANTAGONIST, and manifestations of the human desire for harmony and unity. Less vicious than Shadows, but still happy to try to assimilate whatever gets in their way. As with Shadows, classifiable into types by form and arcana, though they're typically more humanoid: the various classes bear some resemblance to Jungian archetypes. Their native form, parallel to the Shadows' formless black blob, is a floating crystalline prism.

(Possibility: the prism projects the form of the particular Shadow, and shatters when defeated?)

Reflections (? 映像 eizou): Shadow-like beings, distinguished in human form from their Shadow and human counterparts by their silver eyes. Where Shadows are a natural phenomenon, Reflections are specifically created by/awakened by/a direct result of the influence of DIVINE ANTAGONIST. They exist to convince humanity in general, particularly those whose egos are powerful enough to put up significant resistance (i.e. Persona-users), to give up their selves and join the collective within Utopia.

Velvet Room: The Velvet Room fits poorly into the official understanding of this system, especially since only a few people have been able to access it in the past. In reality, it is a sort of individualized 異世界, a small chunk of that form shaped by both Igor and the person to whom that particular manifestation of it "belongs". The assistant is a manifestation of the anima/animus of the "owner", and both they and Igor offer advice and insights to the character. (After all, wild cards or not, they did technically enter into a contract.) While the nature of these beings is unknown, the yellow eyes of the assistants hint at a link to Shadows.

Past Canon
Dark Hour (影時間 kagejikan): A temporal 異世界, created during the course of the disastrous experiments at Port Island some 20 years ago. No longer extant, but theoretically capable of being induced again.

TV World: The "main" 異世界 and native home of the Shadows; theorized to be a manifestation of the collective unconscious. Many paths to it exist beyond simply the TV (a currently unusable method anyway), and many realms exist within it. The main setting for official Shadow research.