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.
The document number is the passport number, which can be but not necessarily include alphabets. It commonly consists of between six and nine alphanumeric characters, meaning it can be made up of numbers, letters or a combination of both. The passport number is often used as a form of personal identification and is valid in countries which recognise the document. As such, this document number can be used to confirm your identity, your citizenship and your immigration status.