Good question

We use 'however' as a conjunctive adverb showing contrast that we forget that it has another function: to express
extent. Let's have a look:

1. However much he prepped, he couldn't get a perfect score.

2. We must address all the concerns, however trivial some may be.

3. However, may concerns are of paramount importance and must be dealt with immediately.

The first two sentences use 'however' to express extent. When 'however' is used in this way it does not require a comma immediately following it. If 'however' is used to show contrast, as in sentence 3, then it needs a comma immediately following it.

Hope that clears up any confusion
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Christopher Lele
Magoosh Test Prep

@devinawilliams83

It actually gets a little tricky if you use 'however' as a subordinate conjunction. If you join to independent clauses - as you did - then you must use the semi-colon with however. You must also put a comma in front of however, the way you would when however is used as a subordinate conjunction the beginning of the sentence.

He likes to go to market; however, he will not go this week.

Another important thing: however, when used as a Sub. Conj. can also go near the beginning of the sentence.

The man with the dog, however, could not dine at the restaurant.

Notice that 'the man with the dog' is not a dependent clause. Therefore ', however,' is correct and you do not need to use a semi-colon. Besides the placement of 'however,' this sentence is no different from:

However, the man with the dog could not dine at the restaurant.

Where a writer put the 'however' depends on the rhythm of the sentence. However, it is important to note that some grammar sticklers (influenced by Strunk and Whites Elements of Style), believe it is incorrect to start a sentence with 'however', when however is used as a subordinate conjunction.

The GMAT, however, does not subscribe to this "orthodoxy." I just thought I'd point this out because a google search on 'however' can yield conflicting info.

Hope that helps!
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Christopher Lele
Magoosh Test Prep