Today's English lesson

From the American Heritage Book of English Usage:

Ne plus ultra

You get the knife, the bowl, and the book. Plus you get the free knife sharpener.

The use of plus as a conjunction connecting clauses or starting a sentence that emphasizes an additional thought occurs frequently in sales pitches, but it is not well established in formal writing.

The use of plus to connect nouns presents a more complicated issue. When equations involving addition are written out in words, the verb is usually singular:

Three plus two is five.

Similarly, when plus connects nouns or noun phrases, the verb is usually singular:

Their strength plus their intelligence makes them formidable opponents.

Some people would argue that in these sentences plus functions as a preposition meaning “in addition to,” but if this were true, you would be able to move the plus phrase to the beginning of the sentence, and this is clearly impossible. You cannot say

Plus their intelligence, their strength makes them formidable.

It makes more sense to view plus in these uses as a conjunction that joins two subjects into a single entity requiring a singular verb by notional agreement, just as and does in the sentence

Chips and beans is her favorite appetizer.