The conjunction “or” can be used not only to indicate two or more alternatives but also to indicate synonymous or equivalent expressions. When used for the latter purpose, “or” can be translated as “also referred to as,” “defined as,” or “in other words,” and sentences containing such an appositional “or” are punctuated differently than sentences in which “or” separates alternatives. Let’s look at some examples.
Infrared spectroscopy or electron paramagnetic resonance spectroscopy can be used to follow the kinetics of radical decay.
Here “or” is used to indicate two alternative techniques—infrared spectroscopy and electron paramagnetic resonance spectroscopy—either of which can be used to follow the decay kinetics. In this type of sentence, “or” separates the two parts of a compound subject, and no additional punctuation is required. What about the following, apparently similar sentence? Continue reading Appositional “or”