Input: Identify the most salient words:

sun disappears from horizon on forest floor

Output: disappear
horizon
sun

Input: Identify the most salient words:

silhouette of bare tree on a mountain

Output: mountain
silhouette
tree

Input: Identify the most salient words:

Skiers at top of slope overlooking valley below.

Output: overlook
skier
valley

Input: Identify the most salient words:

flight over republic outside the plane window leaving a city .

Output:
city
leave
window