Martial art or arts

[99bottles]

When something is related to martial arts, is the compound word we use before the noun martial arts or martial art? I have seen examples of both...
https://en.wikipedia.org/wiki/Category:Martial_art_techniques
https://www.chicagotribune.com/feat...-slmwnzybyjgezfpxnlwhfhb67y-photogallery.html

 

[5jj]

The plural form appears to be much more commonly used: Ngram.

 

[Tdol]

And even more so if we hyphenate the compound.

 

[99bottles]

And even more so if we hyphenate the compound.

By the way, is the hyphenated form the correct form?

 

[Tdol]

I would, but times are changing- what is correct today may not be correct in a few/several years.

 

[Rover_KE]

By the way, is the hyphenated form the correct form?

You can accept both forms.

The 'correct' form of tomorrow, for example, used to be to-morrow.