Conversation so far:
where is delhi located in india outline map
What is the population of Delhi
Delhi has an estimated 2016 population of 18.6 million.
What is the language spoken in Delhi
Hindi is the most commonly spoken language (81%), followed by Punjabi (7%) and Urdu (6%).
What city  in the world compares to Delhi in regards to population growth
According to the report World Urbanisation Prospects 2018, the population of Delhi is now estimated to be 29 million, second only to Tokyo.

Question: Which one is ranked third in the world
Self-contained rewrite: which city is ranked as third most populated city in the world