At once and Once only

At once

At once adverb - Without delay or hesitation; with no time intervening.

Once only and at once are semantically related. In some cases you can use "Once only" instead an adverb phrase "At once".

Once only

Definitions of At once not found.

At once and once only are semantically related. Sometimes you can use "At once" instead an adverb phrase "Once only".
Cite this Source
Once only and At once. (2016). Retrieved 2026, July 29, from https://thesaurus.plus/related/at_once/once_only
At once & Once only. N.p., 2016. Web. 29 Jul. 2026. <https://thesaurus.plus/related/at_once/once_only>.
Once only or At once. 2016. Accessed July 29, 2026. https://thesaurus.plus/related/at_once/once_only.
Google Ngram Viewer shows how "at once" and "once only" have occurred on timeline