Semicolons    ;

Semicolons are “super commas.”

Main rule: Use semicolons to connect complete sentences:

 The rotor turns, and it creates an electromotive field.

 The rotor turns, and thus it creates an electromotive field.

 The rotor turns ; thus it creates an electromotive field.  çsemicolon

    Note:  The rotor turns, thus creating an electromotive field. (No semicolon: "thus creating an emf" ≠ a sentence)

Rule:

Use a semicolon to replace  and + a comma.

Use a semicolon when you are combining sentences with conjuncts: however, therefore, thus, consequently, . . . .

 You need to use semicolons to combine complete sentences that use words like therefore, however, consequently, thus....

The problem of acid rain has become critical, and therefore we need to install scrubbers. çno semicolon

The problem of acid rain has become critical ; therefore , we need to install scrubbers. ç semicolon

The project was complete, and we were glad to move on to something new.

The project was complete ;  we were glad to move on to something new.  çsemicolon

            Note: can you use a comma here?  No, then you have a comma splice.

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Another use of semicolons:

We are opening new branches in Santa Fe, New Mexico; Missoula, Montana; and Moscow, Idaho.

The members of the committee include Jim Jensen, architect ; Bob Hanson, civil engineer ; Greg Cook, electrical engineer ; and Mary Storm, project supervisor.

Rule:  Use semicolons for clarity to set off phrases that already contain commas.