Populace vs Population

Question

What's the difference?

I was writing an essay, which got corrected and i wrote this:

For this reason, sports facilities would have a bigger impact because they would help in mitigating the effects of diseases in the populace, thus saving money because of fewer people being sick.

and it was corrected to this.

For this reason, sports facilities would have a bigger impact because they would help in mitigating the effects of diseases in the general population, thus saving money because of fewer people being sick.

Answer 1

The difference is mostly related to the context in which each is used.

Both words, population and populace, derive ultimately from a Latin word for people, but the words entered English with distinctive meanings. From the beginning, population referred to the collective inhabitants of a place, whereas populace had the meaning “ordinary people” as opposed to the titled, wealthy, or privileged classes ... Not only did the word populace refer to the less privileged part of the population, it was also used as a pejorative term for “the mob, the rabble, the unthinking masses.” source

In things like scientific articles or any similar context when talking about some subgroup of people, use "population" or "general population" instead of "populace".

In the United States, researchers calculated that up to 15% of the general population are at risk of developing heart disease over the next ten years.

Because of its nuanced meaning, I recommend not using "populace" until you fully understand where it is appropriate. For example:

The jury quickly agreed on a verdict of not guilty, and the acquittal was greeted by the populace with shouts of triumph.

In modern writing it may be more common to refer to "the people" rather than "the populace".

It is doubtful that Mr. Nixon or any other thoughtful person could accept "what the people will support" as a valid basis for foreign policy decisions.

Answer 2

This seems really nitpicky to me, but "general population" is arguably a better fit here. However, this is quite a minor difference and I doubt the average native speaker would have any trouble understanding either version.

Merriam-Webster provides this usage note under "Did you know?":

Populace is usually used to refer to all the people of a country. Thus, we're often told that an educated and informed populace is essential for a healthy American democracy. Franklin D. Roosevelt's famous radio "Fireside Chats" informed and reassured the American populace in the 1930s as we struggled through the Great Depression. We often hear about what "the general populace" is thinking or doing, but generalizing about something so huge can be tricky.

The word "population" by itself also has this meaning of the entire group as a whole (as a denotation instead of a connotation), but the adjective "general" explicitly removes this denotation:

5 a : applicable to or characteristic of the majority of individuals involved

Since you're not claiming that every individual is affected by diseases, "the general population" is slightly preferable to "the populace." You could have said "the general populace" as well, but that's less idiomatic than "the general population" or "the general public."