This part of the series (II.a) will deal primarily with those introductory adverbial elements that consist of a single word, rather than a phrase or a clause.
An introductory adverbial element can be a word,a phrase, or a clause.
If it is a single word, it may be a sentence adverb--an adverb that modifies the entire sentence (or clause) rather than just the verb of the sentence (or clause). An introductory sentence adverb is usually set off by a comma.
Ironically, the fires were brought under control just two days before the heavy rains started.
Remarkably, he never understood why all his erstwhile friends had turned against him.
Often the introductory adverb modifies just the verb, as does the word "often" in this sentence. When that is the case, a comma is usually not necessary, but sometimes the writer may prefer to use the comma for emphasis or to create a dramatic pause. Notice the different effects produced by including or omitting the comma:
--Often the introductory adverb modifies just the verb, as does the word "often" in this sentence.
--Often, the introductory adverb modifies just the verb, as does the word "often"in this sentence.
As a general rule, however, it is best to avoid weighing your sentences down with permissible but unnecessary commas. Today's preferred style is uncluttered and expeditious, and most readers consider portentous pauses to be as annoying as speedbumps. Therefore, consider commas after introductory adverbs of this sort to be a heavy spice, to be used sparingly.
Another type of introductory single-word adverb is the conjunctive adverb. A conjunctive adverb frequently functions as a sentence adverb, but it also has a "joining" (conjunctive ) quality that points back toward the preceding clause or sentence. In addition to the single-word conjunctive adverbs, there are also a number of phrases that act as conjunctive adverbs. The guidelines for comma usage that apply to single-word conjunctive adverbs are also valid for phrases that serve as conjunctive adverbs. Here are some of the most common conjunctive adverbs:
There is no unvarying rule for whether or not to use a comma after a conjunctive adverb. Consider the strength or weakness of the conjunctive adverb in relation to the clause that it modifies. If it is weak, omit the comma. If it is of middling strength, use the comma or omit it, depending on the strength of the pause you wish to signal. Often a longer conjunctive adverb seems to need a comma, while a shorter one does not.
~I have left all my studying until the end of the semester; thus I find myself cramming all night, but remembering almost nothing the next day.
~I know better than to get myself into such a bind; nevertheless, I can't seem to break the habit of procrastination.
~Kansas has few prominent landforms to block weather patterns; therefore, one must be prepared for sudden and sometimes very drastic changes in the weather.
~Kansas has few prominent landforms to block weather patterns; thereforeone must be prepared for sudden and sometimes very drastic changes in the weather.
It sometimes happens that a single introductory modifying word will be adjectival rather than adverbial--as when a participle is used to introduce a sentence or clause. In that case, set the introductory modifier off with a comma.