2 clarified the intended question, made uniform the use of "defence" in the post
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What is the difference between an opening and a defence?

I would like to know what iswhy some openings are called defense"defences" and openingother all called "openings." What is the difference?

What is the difference between opening and defence?

I would like to know what is called defense and opening.

What is the difference between an opening and a defence?

I would like to know why some openings are called "defences" and other all called "openings." What is the difference?

1
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What is the difference between opening and defence?

I would like to know what is called defense and opening.