noun
plural ones
[count] :the number
[count] US :a one-dollar bill
[noncount] :one o'clock
[count] :the first in a set or series
as one
formal
at the same time :all together
in agreement with each other
at one with
in a peaceful state as a part of something else
formal :in a state of agreement with another person
for one
as an example
in one
combined in a single thing
the odd one out
pronoun
that person or thing
This sense of one can be used in the plural form ones.
someone or something that is a part of a particular group - + of
a somewhat formal :people in general :any person
b Brit old-fashioned :I or we
one after another
one and all
old-fashioned :everyone
one by one
separately in a series
one in a million
there's one born every minute
adjective
always used before a noun :having the value of
always used before a noun - used to refer to a single person or thing
a - used before a noun to indicate that someone or something is part of a group of similar people or things
b chiefly US informal - used to emphasize a description
always used before a noun :not known exactly :some
used to indicate that two or more people or things are actually the same person or are the same kind of thing
formal - used before a name to indicate that you do not know the person specified
not used before a noun :in agreement with each other
the one and only
used before the name of a famous person to say that there is no one else like that person