Problem: What are the most important words?
a nomad gathers his herd of sheep and goats in the morning
Answer: herd, nomad, sheep

Problem: What are the most important words?
patterned white clouds in a blue sky over a rippled azure sea
Answer: cloud, ripple, sky

Problem: What are the most important words?
an used car that may interest you is for sale in a city .
Answer:
car, city, sale