i i /ˈaɪ/

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
   

 I

noun

1. The 9th letter of the Roman alphabet  ( I )
   the 9th letter of the Roman alphabet
   
2. 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
   
3. A nonmetallic element belonging to the halogens; used especially in medicine and photography and in dyes; occurs naturally only in combination in small quantities (as in sea water or rocks)  ( atomic number 53 , I , iodin , iodine )
   a nonmetallic element belonging to the halogens; used especially in medicine and photography and in dyes; occurs naturally only in combination in small quantities (as in sea water or rocks)
     Iodine is an essential element for the production of thyroid hormones.
   Iodine is an essential element for the production of thyroid hormones.
   
   

pronoun

1. () First person singular pronoun, referring to the speaker.  ( I )
   First person singular pronoun, referring to the speaker.