Essential, Non-essential, and the Comma

Even if there is no need for a colorful design on a surfboard since it won’t change the basic utility of the board, it is often nice to have one anyway (maybe stylized birds or fish in shades of green, yellow, and blue with a few strong black or red lines for a sharp contrast) .

In sentences, some information is like a surf board design, extra bits of information added for interest but not necessary for the basic meaning of the sentence. There is, big surprise here, a punctuation rule for essential and non-essential phrases and clauses, AKA restrictive/nonrestrictive clauses or phrases.

To quickly determine whether or not to punctuate a clause or phrase, one rule of thumb, so to speak, might be to just place your thumb over a group of words in a sentence, perhaps qualifying adjective or adverb phrases or clauses with colorful descriptions. If the sentence reads clearly and makes perfect sense without the group of words covered by your thumb, then set off the temporarily hidden words with commas. The clause or phrase is not essential and doesn’t restrict the meaning of the sentence. A couple of examples - destined, I hope, to appear in my mind soon - should help clarify all I’ve said so far:

The sunlight glinting on the waves, much like tiny touches of starlight, fascinated her. (Nonrestrictive, Nonessential)

The sunlight glinting on the waves fascinated her because it reminded her of starlight. (Essential, Restrictive)

In the second example, a necessary reason is given for her fascination – because it reminded her of starlight. In the first, the same idea of starlight is not necessary for the sentence to make sense, although it also tells the reader why she was fascinated.

See you next time the breeze is cool, the sun is up, and the waves roll into view! ‘Til then, hang ten!