Input: Identify the most salient words:

aircraft operated by military unit

Output: aircraft
operate
unit

Input: Identify the most salient words:

a passenger train makes its way over a bridge above a makeshift cinema in the old quarters .

Output: bridge
train
way

Input: Identify the most salient words:

autumn leaves floating in a water

Output: autumn
leave
water

Input: Identify the most salient words:

the number of neutrons that atoms of a given element contains can vary .

Output:
atom
element
number