This is the 12178th most frequent French word.
vieillissent
"Vieillissent" means "grow old" or "age."
Here, 'vieillissent' refers to the natural process of aging experienced by trees.
Les arbres vieillissent lentement dans cette région.
The trees age slowly in this region.
In this sentence, 'vieillissent' represents the gradual deterioration over time of the buildings.
Les bâtiments historiques vieillissent car ils ne sont pas entretenus.
The historic buildings are aging because they are not maintained.
This use of 'vieillissent' highlights the biological aging process among dogs in comparison to humans.