It seems ironic to be defining the term 'dictionary,' but here we go! Dictionaries are resources for finding word meanings, parts of speech, word origins and even synonyms and antonyms. Dictionaries have definitely evolved over the years. The English language really began with the Anglo-Saxons in Great Britain.
If it is a US Passport, that it is the 9 digit number located in the top corner of the passport info page. In the example below the passport number is 31195855. Other Countries have different types of numbers (usually with letters added) but most often it's in the same place. This Canadian Passport number is AB504966.
It is the 9 digit number in the upper-right hand corner of the main page of your passport-the one with your picture and information in it. At least in my mid-2000s passport book.