o (EN)
letter, numeral

This word can also be a form of:
O (letter, noun, particle, Proper noun, symbol)

letter “o”

o
  1. the lowercase form of the letter "O"
    The word "octopus" starts with the letter "o".

numeral “o”

o
  1. zero, especially when saying numbers aloud
    My flight number is four-o-six (406).