Using commas with appositives

An appositive is a noun or noun phrase that elaborates or describes the noun to which it is next.

Often, an appositive is parenthetical, i.e. it could be omitted without changing the basic meaning of the sentence. Here, we put commas around the appositive:

• Head of department at AU in Herning, Anders Frederiksen, is excited about the new project.

However, an appositive can also be identifying, i.e. non-parenthetical, in which case no commas should be placed around the addition:

• The department’s centre ‘Manufactory’ will bridge the gap between knowledge and production.

In the above example, no commas are put around ‘Manufactory’, because the name is essential for conveying the meaning of the sentence. Essential in the sense that it is important to know which centre at AU in Herning we are referring to.

Consider the following sentences:

• Her brother Michael teaches and conducts research on business models.
• Her brother, Michael, teaches and conducts research on business models.

In the first sentence (without commas), Michael is one of several brothers, while in the second sentence (with commas), Michael is the only brother.

The presence or absence of commas with appositives can therefore lead to a difference in meaning. In other words, you need to have the relevant background knowledge to be able to place commas correctly.