one day

Adverb

one day

1. (set phrase) At some unspecified time in the future.
   • One day I shall upgrade my software, but not just yet.
   • This was a voluntary charter flight, not an ICE enforcement operation. All participants were offered the same benefits as any illegal alien who self-deports using the CBP Home App. They received travel assistance, a $1,000 stipend, and preserved the possibility they could one day return to the...2025 May 19, “Project Homecoming Charter Flight Brings Self-Deporters to Honduras, Colombia”, in Department of Homeland Security

   Synonyms:

   one of these days, some day

2. At some unspecified time in the past.
   • One day I was playing with a girl from my class.
   • One day I was out in the barn and he drifted in. I was currying the horse and he set down on the wheelbarrow and begun to ask questions.1913, Joseph C[rosby] Lincoln, chapter XI, in Mr. Pratt’s Patients, New York, N.Y.; London: D[aniel] Appleton and Company, →OCLC

   Synonyms:

   once

3. Used other than figuratively or idiomatically: see one, day.
   • You can stay one day or two.

   Synonyms:

   byembye, hereafter, in the future, later, later on, one of these days, one of these fine days, someday, sooner or later