It was the two countries' mutual agreement that allowed them to expand their economy exponentially.
(this is a plural possessive, as shown by the apostrophe)
see How do you put the word countries in a sentence?
Countries' is a plural possessive, meaning "belonging to the countries." The countries' rulers met to discuss the treaty.
The desire of changement in youths is changing the developing countries. This is a sentence containing the word changement.
It was my destiny to help children in third world countries.
When you go to some European countries you have to use a euro intead of a dollar.
The countries imports outweighed their exports resulting in a trade deficit.
It is important for developing countries to utilize their natural resources efficiently.
sleap countries SLOGAN is why buy a matress anywhere else
There are 47 landlocked countries in the world, including partially recognized states.
Many countries experience revolution to gain independence from the current regime.
There are many countries in the world
Many countries in Africa impoverish their people, causing an unproductive nation.