When adding a job title or description before or after someone's name, you have to decide whether you need commas. You need two commas if you have inserted a nonessential additional description after your noun. If you feel that your first word or noun in the sentence is specific enough that the reader needs no further information in order to identify it, then a subsequent interruption to give further description should be surrounded by commas, like this:
My only child, Jim, is applying to colleges right now.
The words "my only child" are specific enough to fully identify who I am talking about. They narrow my discussion to one human being. Giving his name is merely additional, nonessential information. The term nonessential refers to whether the information is needed in order to narrow the discussion down to the one person or thing I am talking about.
My cousin Ruth called one day last week.
The name Ruth is essential in this sentence, because I have more than 20 cousins. In my family, the words "my cousin" do not fully do the job of narrowing the discussion down to one person. It doesn't matter whether my readers know that--the fact that I know it is enough. I know that the specific name is needed for precise identification of the person I am talking about.
The File menu, located at the upper left of the screen, contains the Share command.
Here, the words "the File menu" fully identify the exact part of the software being discussed. The additional description "located at the upper left of the screen" is not essential for precisely identifying which screen item you mean.
If you start your sentence with a job title right before a name, don't put a comma between the job title and the name, and don't put one after the name, either:
Instructional designer Bob Henderson will show us how to plan our lesson.
But if you put the word a or an before the job title, meaning you are using it generically, then you do need the commas:
An instructional designer, Bob Henderson, will show us how to plan our lesson.
If you start your sentence with a description that applies to the subject of the sentence, use just one comma to separate the introductory description from the beginning of the sentence:
Built just last year, the parking structure was already overcrowded.
Challenge: Add or subtract commas to correctly punctuate these sentences
- "Another electrolyte, potassium works with sodium to generate the electrical current necessary for muscle function."
- The president of Super Simplistic Solutions Biff Bifferson, opened the competition to clients as well as staffers.
- A nurse's aide Jon Boxco, greets each patient at the desk.
- "Important for bones and teeth, this element is even more essential in cell physiology."
- Ramakrishna Sing, a research associate at the National University created a new way to purify water.
- Administrative associate, George Baker, set up the new device.
- Built just a year ago the senior center is already full.
Answers to the prepositional phrase challenge are brought to you by Karyn R. Smith, except for the second one in number 5, which is brought to you by Elisia Getts.
- The pigeons [on the balcony] ate the leaves off [of the chrysanthemum]. Adjective; adjective.
- [Because of the sudden noise], the birds all flew [from the railing] [at once]. Adverb; adjective; adverb.
- [High atop the chimney] is [where the mocking bird] liked to sing. Noun; noun.
- The eagle soared [over the building] and [out across the open plain]. Adverb; adverb.
- [During the rainstorm], the cats huddled [under the porch]. Adverb; adjective.
- [After the quiz], we will return [to the main body] [of the eLearning lesson]. Adverb; adverb; adjective.