The formless realm is one of the three realms, said to be a world that transcends physical form.
In Buddhist teachings, deep meditation is necessary to be reborn in the formless realm.
欲界 is the realm of desire, the lowest of the three realms, characterized by attachment to sensory pleasures, in contrast to the formless realm.
色界 is the realm of form, where beings have subtle bodies but are free from gross desires, situated between the desire realm and the formless realm.
From 無色 (formless) + 界 (realm, world). A Buddhist term translating Sanskrit ārūpyadhātu.