Exciting news! With our new Ad-Free Premium Subscription you can enjoy a distraction-free browsing experience while supporting our site's growth. Without ads, you have less distractions and enjoy faster page load times. Upgrade is optional. Find out more here, and enjoy ad-free learning with us!
:up: Precisely; hence the use of the definite article. This 'the five boroughs' is geographically precise, rather as 'the Square Mile' is a precise reference to the City of London (about a square mile - the financial district that (until recently) was the main area for banking in London).