Within a farewell to arms, what would be the best definition of the word “regiments”?

The correct answer is, a Regiment is a unit in the Army. Specifically is a unit of forces on the ground that has battalions or units that support the Regiment and have their own headquarters.

“A Farewell to Arms" is a novel written by Ernest Hemingway that was published in 1929. The novel is located in Italy and Switzerland during World War I and refers to the war told by the Italian side. The main character is Frederick Henry, and he describes his life in the war and his affair with an English nurse called Catherine. He met the girls in Turin, Italy.

the anwser is went creeping down the river again, across the wide lonely marshes to the sea.

i longed to go with them out into the world to seek my fortune in foreign lands—africa, india, china and peru!

and, dreaming of the lands i had never seen, i'd sit on there, watching till they were out of sight.