one one /ˈhwʌn/

adjective

1. () Used of a single unit or thing; not two or more  ( ane [Dialect, UK] , i , 1 , one )
   used of a single unit or thing; not two or more
    Ane' is Scottish
   ane' is Scottish
   
2. () Having the indivisible character of a unit  ( unitary , one )
   having the indivisible character of a unit
    A unitary action
   a unitary action
    Spoke with one voice
   spoke with one voice
   
3. () Of the same kind or quality  ( one )
   of the same kind or quality
    Two animals of one species
   two animals of one species
   
4. () Indefinite in time or position  ( one )
   indefinite in time or position
    He will come one day
   he will come one day
    One place or another
   one place or another
   
5. () [Informal] Very; used informally as an intensifier  ( right [Informal] , one [Informal] )
   very; used informally as an intensifier
    That is one fine dog
   that is one fine dog
    A right fine day
   a right fine day
   
6. Eminent beyond or above comparison  ( matchless , nonpareil , one , one and only , peerless , unmatchable , unmatched , unrivaled [American] , unrivalled [Canadian, British] )
   eminent beyond or above comparison
    Matchless beauty
   matchless beauty
    The team's nonpareil center fielder
   the team's nonpareil center fielder
    She's one girl in a million
   she's one girl in a million
    The one and only Muhammad Ali
   the one and only Muhammad Ali
    A peerless scholar
   a peerless scholar
    Infamy unmatched in the Western world
   infamy unmatched in the Western world
    Wrote with unmatchable clarity
   wrote with unmatchable clarity
    Unrivaled mastery of her art
   unrivaled mastery of her art
   
7. Being a single entity made by combining separate components  ( one )
   being a single entity made by combining separate components
    Three chemicals combining into one solution
   three chemicals combining into one solution
   

noun

1. () The smallest whole number or a numeral representing this number  ( I , single , unity , 1 , ace , one )
   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
   he has the one but will need a two and three to go with it
    They had lunch at one
   they had lunch at one
   
2. () A single person or thing  ( one )
   a single person or thing
    He is the best one
   he is the best one
    This is the one I ordered
   this is the one I ordered
   

pronoun

1. () Referring to any individual in a general sense.  ( one )
   Referring to any individual in a general sense.
   
2. () Referring to a specified entity or object.  ( one )
   Referring to a specified entity or object.