Problem: What are the most important words?
a town an ancient city in the southwest of country hewn from towering walls of rock
Answer: city, country, rock, tower, wall

Problem: What are the most important words?
steel and glass frame of the modern house extends the living space outdoors
Answer: extend, house, live, space

Problem: What are the most important words?
cargo ships float in the sea .
Answer:
float, sea, ship