Correct spelling, explanation: troops is a word of Latin origin and more precisely it comes from the word troppus, which had the meaning of flock. Later, the word appeared in French, too, in the form of troupe. When it comes to English, troops didn’t appear in it until the 16th century. Today, troops is a plural noun.

Definition of troops:
1. noun – a bigger group of soldiers on duty,
The troops were marching through the woods and singing some heartwarming songs.

Collocations with troops:
Some popular collocations with troops are: armed troops, the withdrawal of troops, and peacekeeping troops.
The government has sent there a division of 3,000 heavily armed troops to protect the civilians.
The moment the two governments reached an agreement, the Prime Minister announced the withdrawal of troops.
The peacekeeping troops were sent to Africa to calm down a growing conflict between the tribes.

Incorrect spelling, explanation: one of the most common spelling mistakes made in the word troops is to write it with a -u letter instead of a double -o letter. The result is the form troups, which is incorrect and, in fact, a word like this doesn’t exist in English. The correct spelling is troops.