Sometimes an apostrophe can make all of the difference. So it is with these words.
“Ma’am” is the correct spelling of the polite address of a woman, as in “Thank you for the change, ma’am.”
“Mam” refers to a member of a Mayan people of southwestern Guatemala or to the language they speak.
______________
My name is Rob Bignell. I’m an affordable, professional editor who runs Inventing Reality Editing Service, which meets the manuscript needs of writers both new and published. I also offer a variety of self-publishing services. During the past decade, I’ve helped more than 300 novelists and nonfiction authors obtain their publishing dreams at reasonable prices. I’m also the author of the 7 Minutes a Day… writing guidebooks, four nonfiction hiking guidebook series, and the literary novel Windmill. Several of my short stories in the literary and science fiction genres also have been published.