The English terms the Dreaming and the Dreamtime entered use through anthropologists working in central Australia in the late nineteenth and early twentieth centuries, rendering the Arrernte word altyerre. They were then applied to comparable but distinct concepts across the continent: Jukurrpa in Warlpiri, Ngarrankarni in the Kimberley, Wongar among Yolngu peoples, Tjukurpa in the Western Desert, and many more. The words are not synonyms and the concepts do not map onto one another exactly.
The English term also imports two things that are not in the originals. The first is sleep. The connection to dreaming in the English sense is at best partial, and many communities regard it as misleading. The second is time. "Dreamtime" suggests an era that finished, whereas the concepts generally describe something that is ongoing and present, established when ancestral beings shaped the land and continuing to operate in it now. Country is not a record of past events; it is where those beings are.
What the concepts do broadly carry is a unity of origin, law and land. The ancestral beings travelled, made the landforms, water, species and people, laid down the rules under which people live, and remained in the country in one form or another. Ceremony, song and design maintain that arrangement rather than commemorating it, and neglecting them is understood to have consequences for the country itself.
Many communities now prefer their own language terms, or use "the Dreaming" only when speaking to outsiders. Using the local word where it is known is more accurate and is generally what the people concerned would rather see. Where this encyclopedia uses the English term, it is a convenience for readers and not a claim that one concept lies behind it.