1. [n]  position 18 in a countable series of things
2. [adj]  coming next after the seventeenth in position

EIGHTEENTH is a 10 letter word that starts with E.

1. \Eight"eenth`\, a. [From {Eighteen}.]
   1. Next in order after the seventeenth.
   
   2. Consisting of one of eighteen equal parts or divisions of
      a thing.
   
   

2. \Eight"eenth`\, n.
   1. The quotient of a unit divided by eighteen; one of
      eighteen equal parts or divisions.
   
   2. The eighth after the tenth.