How are you managing with my comma compilation so far?
Needless to say, there is more.
Some words, such as who, which, and whose, bring comma-plications of their own.
Essential or nonessential information?
Whether you use a comma or not often depends on whether the clause is essential to the sentence, or nonessential.
The footballer, who had trained with the Academy, joined the Wanderers.
This sentence makes sense without the middle phrase. It is nonessential, so bracket it between commas.
Added information requires added commas.
The footballer who had trained with the Academy joined the Wanderers.
In this sentence, that same phrase is essential in order to identify the person (or thing). Essential information is not added information, so you don’t need added commas.
This principle – that added information needs added commas – was gleaned from an American website that often comes up in my searches. Grammar Girl at https://www.quickanddirtytips.com/education/grammar is easy to understand and often includes handy tips to help you remember.
Sometimes US grammar terms differ from UK terminology but I rarely try to remember jargon anyway. You don’t need to name a principle to understand and apply it.
Grammar Girl articles usually point out where UK practice differs from American (also helpful) but both sides of the Atlantic seem to agree about commas.
The principle of added commas for added scraps of information can also apply to other categories of comma. Take, for example, these enclosing commas.
I went to see Jane Fonda’s latest movie, ‘Book Club,’ with my boyfriend, Bill.
Here, a comma is needed in the second sentence after ‘movie’ (because the movie has already been identified; this and only this is Jane Fonda’s latest movie). It’s also needed before ‘Bill’, because he and only he is the writer’s boyfriend (unless she’s a lucky girl). Neither phrase is essential to the meaning of the sentence; both are added information and require added commas.
I went to see the movie ‘Book Club’ with my boyfriend Bill.
Here, the whole sentence is essential to convey the sense of the statement; we’re talking about a specific film and a specific person.
But in the first sentence, the names (eg. ‘Book Club’, ‘Bill’) are the only things in the world described by the preceding identifier (ie. ‘latest movie’, ‘my boyfriend’). They are added window-dressing – nonessential – and need a comma before each one (and after it as well, unless it’s at the end of the sentence).
Consider these examples…
My son, Paul, is a bricklayer.
This is correct if you have one son; the name is not essential – it’s added information. But if you have more than one son…
My son Paul is a bricklayer.
…the name is essential to the meaning of the sentence and needs no commas.
Of course, it isn’t quite that easy… if the identification comes after the name, it should always be surrounded by commas.
Paul, my son, is a bricklayer.
When your head stops spinning, there are numerous websites and blogs more qualified than I to go into further detail. Here are another three of the sites I plundered for these articles.
An online search will bring up many more.
Words that end in ‘…ing’
Should there always be a comma in front of them?