Because & the Comma & 3 Items in a Series

[gjo123]

My question has two parts:

(1) when a "because" clause does NOT introduce the sentence, how do I determine whether I am to use a comma in front of it or not?

(2) is it true that the current trend among grammarians is to place a comma following the second item in a series of three items? I often see the comma omitted before the next to the last item in the series.

[svartnik]

My question has two parts:

(1) when a "because" clause does NOT introduce the sentence, how do I determine whether I am to use a comma in front of it or not?

(2) is it true that the current trend among grammarians is to place a comma following the second item in a series of three items? I often see the comma omitted before the next to the last item in the series.

1. When a dependent clause starting with "because" is placed first in a sentence, use a comma between the two clauses. When an independent clause is placed first and the dependent clause second, do not separate the two clauses with a comma.

2. No. The comma before the last item in a sequence of items changes the meaning.

Example:
a. I will visit X, Y, and Z.
b. I will visit X, Y and Z.

a. means three persons and three different houses
b. means 3 persons and two houses: Y and Z live together

[David L.]

The comma before the final 'and' is used to prevent some forms of ambiguity, and is known as the Oxford comma in the UK, and Harvard comma in the US.
(It doesn't remove all ambiguity, but it helps!)

"I bought apples, pears, and bananas."
Here, omission of the comma would not affect the clarity - pears and bananas are clearly two different fruits.

"We ordered soup, bangers and mash, and cheese and biscuits."
Here, the use of commas keeps it clear: what was ordered, and what items were served together.

With:
b. I will visit X, Y and Z.
b. means 3 persons and two houses: Y and Z live together
Let's change that to:
"I will visit Tom, Barry and Paul"
It is NOT clear whether this refers to three visits; or two, because Barry and Paul live together. To state the latter clearly, we would have to write:
"I will visit Tom, and Barry and Paul."
Commas come and go, depending on whether you follow the Oxford/Harvard option or not. Two 'ands' do not occur without a definite purpose of indicating association, as in 'bangers and mash', and 'cheese and biscuits'.