Hi. I think whether they be called conjunctive adverb or sentence adverb ( I don't know what they exactly mean), it is safe to say they are adverbs in general.

Let me give you what I think is an adverb, "perhaps."

Let me also give you what I think is a conjunctive adverb. I think we consider conjunctive adverbs sentence adverbs. I think sentence adverbs are the ones that modify a sentence as a whole.

The conjunctive adverb is "for instance."

If I put the word "perhaps" in front of the sentence or clause, I think it wouldn't normally be followed by a comma, but if we put the words "for instance" in front of the sentence, I think a comma would be followed. Why is that (if there is a reason)?


Perhaps it is vague.

For instance, it may not be so clear.
Anonymous Perhaps it is vague.
I'm sure you'll get plenty of replies to your question. I'm not conversant with these special adverb terms, but I see nothing special about the captioned example.

Often it is vague.
It often is vague.
It is often vague.
It is always vague.
Always it is vague.

This seems the same as "perhaps," and answers the question "when."

I eat slowly.
I eat often.
Often I eat.
Perhaps I eat.

Perhaps if I knew your definitions, I'd see this in a different light.
Sorry, I now realize that you offered "perhaps" as an example of a normal adverb. Somehow I missed it. (But I don't see the need for a comma.)

I hope someone will address your question about the "conjunctive / sentence adverb."
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Just as an aside:

Transitional words=conjunctive adverbs, such as however, moreover, nonetheless, nevertheless, etc.

Transitional expressions=in fact, in addition, needless to say, etc

All of these words are transitions; that is, they join sentences, clauses, and paragraphs together.

Treat all these expressions as parenthetical elements. The rule is that you place commas around parentheitcal information, so you do the same with these expressions. However, if they are situated next to a coordinating conjunction, place a comma around the two words but not around the transitional expression itself.

I went to my favourite shopping mall, and therefore, I spent all my money.

I went to my favourite shopping mall, and, therefore, I spent all my money.

I went to my favourite shopping mall, and therefore, I spent all my money.

I might write this in several different ways, but this isn't one of them.

I don't feel that these are places where I would naturally pause in speech.

Best wishes, Clive

Hi, Clive,

I thought we established a long time ago that I use commas in accordance with the rules of grammar, whereas you use them based on common sense and how you wish the sentence to be conveyed.

Rule: place commas before a coordinating conjunction (and) which joins two independent clauses.

Rule:When a coordinating conjunction is placed next to parenthetical elements, the comma does no longer surround just the expression.

Personal preference: Place commas where you want the reader to pause to help convey the sentence's meaning.

I just feel if we don't have rules, then things can get sloppy. Thus I abide by rules. (And yes it is boring, and yes, rules can be broken).

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Play it the way you see it.

Best wishes, Clive