In our discussion of comma use, we have examined commas with elements like contrasting expressions and direct address. These can be considered interrupting expressions, which, as Joseph Blumenthal states, are asides from our main thoughts: “In speech, we keep such expressions in the background by dropping our voice and pausing before and after; in writing, we use commas” (English 3200).
They are also known as parenthetical expressions, which are explanatory or supplemental or transitional words and phrases added to sentences either to make the meaning clearer or more emphatic. Another interrupting expression is the transitional expression, which connects sentences to the preceding ones. As we have seen with the previous posts, these can be removed without damaging the meaning or completeness of a sentence.
Here are some common parenthetical and transitional expressions:
|however||of course||for example||after all|
|therefore||by the way||nevertheless||if possible|
|perhaps||you know||on the whole||on the other hand|
|it seems||I suppose||on the contrary||generally speaking|
Richard Nordquist identifies some of these phrases as comment clauses or tags, “short word groups, such as ‘you see’ and ‘I think,’ that add a parenthetical remark to another word group.” These are common expressions heard in everyday speech and used in dialogue to give it a natural tone.
Other words in the list are conjunctive adverbs, transition words or phrases used to connect parts of sentences.
Here are some examples of both types:
The holiday is, in fact, Memorial Day.
The refreshments, by the way, were excellent.
The boys, however, were not acting properly.
Methane is a byproduct of decomposing livestock manure, for example.
As pointed out before, parenthetical and transitional expressions add non-essential information to sentences so that they can be removed without changing the meaning. As such, they are set off by commas – one comma if the expression occurs at the beginning or the end of the sentence, and two commas if the expression occurs in the middle.