Can you please explain the rule of the transition word "however"?

English is not my first language, and I’m having trouble understanding correct transitions with the word “however.”


On our mock ACT the question was:

Snowflakes form from tiny water droplets, following a specific process of chemical bonding as they freeze which results in a six-sided figure. The rare "triangular" snowflake, similarly, confounded scientists for years because it apparently defied the basic laws of chemistry.

F)no change

G)for example,

H)additionally,

J)however,

The correct answer was J.


In another example:

I wasn't planning on going to the wedding, however you've convinced me that it's a good idea.

A. NO CHANGE

B. wedding, however,

C. wedding. However,

D. wedding,

The correct answer was C.


According to the previous example, why is the answer B incorrect?

In the first example, the word "however" is joining two dependent clauses. Neither "The rare 'triangular' snowflake" nor "confounded scientists for years because it apparently defied the basic laws of chemistry" can stand on its own as a sentence. "However" works as a transitional word that joins the two dependent clauses together and transforms them from two sentence fragments to one complete sentence.

In the second example, "however" is instead joining two independent clauses. Both "I wasn't planning on going to the wedding" and "you've convinced me that it's a good idea" are complete sentences in their own right. This presents a slightly different situation. The traditional rule is that if you're using "however" to transition from one independent clause to another, it should either start a new sentence or be preceded by a semicolon rather than a comma. You could also say "wedding; however," but that wasn't one of the choices. That makes Choice C the best option.

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