Is there a single word for 'without a beginning'? [closed]

Is there a single word for: something that has no beginning or without a beginning

beginningless

Collins

having no beginning

Good question. In traditional English theology, the closest concept is eternal, which also implies endlessness. Atemporal implies not existing in time at all. Ageless or timeless can literally mean having no age, but more often imply not showing the effects of time. Words such as primordial traditionally carry the implication of first-created, but in a context that implies anything is eternally ancient, it would mean that instead. I would suggest that immemorial comes closest.

Consider the term unbegotten:

not created; having no beginning; eternal

But this is a word that you're most likely to encounter only in theology. It literally means not brought into existence by the process of sexual reproduction.

Another good word from theology that I can recommend would be uncaused:

not brought into existence by any cause

In the Muslim and Christian religions as well as in Judaism, God is regarded as the uncaused cause of everything that exists. That is, God is the cause of absolutely everything, but he himself was never created which implies that he has no beginning.

Well, 'beginningless' is an obvious phrasing but, given that such a thing doesn't exist outside of thought experiments, it's worth mentioning that the standard philosophical term of art for what you're discussing is the

prime mover, n.

1. A person who instigates or originates something; spec. G-d regarded as the motive force of the universe...

It and 'first mover' are calques of the Latin phrase 'primum mobile' &c. (which is also used in English), translating Arabic al-muḥarrik al-awwal or امحرك الأوّل (which isn't), translating Aristotle's Greek τὸ πρῶτον κινῆσαν (tò prôton kinêsan).

Following Aristotlean logic, some form of self-existent, uncreated G-d was assumed to have been necessary to get the rest of creation moving in order to avoid an infinite regress of causation. As Davislor already mentioned, such a G-d was less eternal than atemporal. If there was any cause for our universe before the Big Bang, it would likewise exist outside the time known within our universe which modern physics suggests came into existence with space.