Punctuation: How commas and semi colons are used in written English?

Can you tell me how commas and semi colons are used in written english?

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BRIEFLY, semicolons serve the same purpose as full stops or coordinating conjunctions; they separate two independent clauses. They draw the ideas of these clauses closer together than do full stops, but not so close as do coordinating conjunctions.

Commas have a multiplicity of uses, but are mainly used to separate grammatical and thought units within the sentence. Google the word ‘comma’ for pages of explanation.
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