One
One adjective - Being the one or ones of a class with no other members.
Once only
One and once only are semantically related in in the past topic. Sometimes you can use "One" instead an adverb phrase "Once only".
Mutual synonyms
Cite this Source
Once only and One. (2016). Retrieved 2026, August 15, from https://thesaurus.plus/related/one/once_only
One & Once only. N.p., 2016. Web. 15 Aug. 2026. <https://thesaurus.plus/related/one/once_only>.
Once only or One. 2016. Accessed August 15, 2026. https://thesaurus.plus/related/one/once_only.
Google Ngram Viewer shows how "one" and "once only" have occurred on timeline