Martial and Marital are easily confused words.
The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It suggests what word you may want to save time, but quite often, its suggestions couldn’t be more off base and produces humorous results.
Martial is an adjective. It describes activities that are related to the military or other defense techniques. For example, “martial arts” is a collective term used in the US for sports like jiu-jitsu, aikaido, tae-bo, and karate. These sports are often taught in a studio by masters.
In another example, “martial law” means the military has taken over the government of a country and ruling that country by their code. Countries under martial law bear some resemblance to dictatorships in that they have rigid guidelines and aren’t receptive to criticism of their rules.
Marital is an adjective. It describes activities and qualities related to marriage.
The following story uses both words correctly:
Marcel was a sworn bachelor. Even as his old friends started to pair off after college, he swore he wouldn’t follow. “Marital bliss? More like martial law,” he wisecracked. “I can come and go as I please and no one limits my freedom.”
Eventually, though, an empty loft and total freedom lost its appeal. No friends were free to hang out anymore. Not a man to mope, Marcel got a dog, got a boat, and sailed around the world.