This is the 6804th most frequent French word.
lamontagne
"The mountain."
Lamontagne is used here as a proper noun, likely someone's name.
Je vois Lamontagne de loin.
I see Lamontagne from afar.
Here, "la montagne" is a common noun referring to a mountain.
La montagne est majestueuse au lever du soleil.
The mountain is majestic at sunrise.
In this case, "la montagne" refers to a physical terrain landmark, a specific mountain.