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one day

one day

1.1
At some time in the future
  • idiom
translation icon : algún día
  • I hope to travel to Europe one day when I have enough money.

And you're going to be a legend one day, not now.

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Examples

  • The mouse family decided one day it would be nice to have a picnic.

    Academic text (2011)
  • Change had this way of sneaking up on you, one day at a time.

    Fiction book (1990)
  • I went there to give a talk one day about the book.

  • So better to take one day, one day at a time.

  • Until one day, when things started to change.

  • If you are doing something special one day, drop them a line and invite them to stop by.

    Academic text (2008)
  • So maybe I will one day, but I'm not ready yet.

  • I'd like to have a house like this one day, and I did.

  • With this help, they may one day be able to watch the Lions play.

  • After they had grown, they decided one day to go on a journey in search of wisdom.

    Academic text (2008)

Synonyms

someday
vsone day
1.0

At some time in the future

has identical meaning and usage in general
sometime
vsone day
791 2.2

At a time that is not known, in the past or future

restricts this to future times only
down the road
vsone day
188 3.7

At a time in the future

covers any unspecified future moment, not only later sequence
soon enough
vsone day
171 1.7

Happens at a time that is early enough, not too late

refers broadly to an unspecified future time without urgency
down the line
vsone day
92 4.4

At some point in the future

is more general, not limited to later ordered points
before long
vsone day
56 1.6

It happens soon

can mean any future time, not necessarily soon
by and by
vsone day
  • Literature
9 7.1

After a while

is neutral about delay and simply names a future time

How Specific

tomorrow
1.0
soon
1.0
one day
1.1
sometime
791 2.2

Surface Forms

one day positive
one-day positive

Morphology

one + day

The meaning 'at some unspecified time in the future' is directly derived from combining 'one' (a single) with 'day' (a day) and understood as 'a single day at some point' (i.e., 'someday'). This adverbial extension is cross-linguistically common and follows normal compositional semantics, so a B1 learner who knows the constituent words will very likely infer the intended meaning.

Etymology

One day uses the simple picture of a single day in the future when something will happen, like circling a date on a calendar but not naming it. So, people say one day to mean 'sometime in the future' or 'someday'.