one

nouns

the smallest whole number or a numeral representing this number
"he has the one but will need a two and three to go with it"; "they had lunch at one"
a single person or thing
"he is the best one"; "this is the one I ordered"
one
is a type of (narrower)
a single undivided whole
"an idea is not a unit that can be moved from one brain to another"

adjectives

used of a single unit or thing; not two or more
"`ane' is Scottish"
having the indivisible character of a unit
"a unitary action"; "spoke with one voice"
is derived from
of the same kind or quality
"two animals of one species"
one
is similar to
closely similar or comparable in kind or quality or quantity or degree
"curtains the same color as the walls"; "two girls of the same age"; "mother and son have the same blue eyes"; "animals of the same species"; "the same rules as before"; "two boxes having the same dimensions"; "the same day next year"
used informally as an intensifier
"that is one fine dog"
one
is similar to
beyond what is ordinary or usual; highly unusual or exceptional or remarkable
"extraordinary authority"; "an extraordinary achievement"; "her extraordinary beauty"; "enjoyed extraordinary popularity"; "an extraordinary capacity for work"; "an extraordinary session of the legislature"
indefinite in time or position
"he will come one day"; "one place or another"
one
is similar to
vague or not clearly defined or stated
"must you be so indefinite?"; "amorphous blots of color having vague and indefinite edges"; "he would not answer so indefinite a proposal"
being a single entity made by combining separate components
"three chemicals combining into one solution"
one
is similar to
made or joined or united into one
eminent beyond or above comparison
"matchless beauty"; "the team's nonpareil center fielder"; "she's one girl in a million"; "the one and only Muhammad Ali"; "a peerless scholar"; "infamy unmatched in the Western world"; "wrote with unmatchable clarity"; "unrivaled mastery of her art"