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Word Usage: Since or Because?

The word since, when used as a conjunction, has two meanings, one related to time and the other to cause. Since can be correctly used in either sense—the choice is a matter of style.

However, if it is not used carefully, the word since can also cause confusion. Sometimes, because is the better choice.

This word usage tip examines when—and when not—to use the word since.


since (conjunction): from the time in the past when

He had wanted to be a biologist since he was 12 years old.

since (conjunction): because

Since the data were incomplete, the paper could not be published.

In the second example above, since clearly means "because." Be aware, however, that the word since can be ambiguous, leaving the reader to sort out whether it means "from the time when" or "because."

In the example below, we understand that the study could not be performed, but has that happened from the time when the equipment malfunctioned (ie, for a period of time)? Or has it happened because the equipment malfunctioned (no time specified)?

The study could not be performed since the equipment malfunctioned.

The study could not be performed because the equipment malfunctioned.

Quick Tips: Since vs Because

Speedy pencil: quick grammar tips

  1. If there is any chance that the reader could think that the word since refers to time when it in fact refers to cause, then use the word because.
  2. Some style guides prefer that writers use the word since to refer only to time.


Iverson C, Christiansen S, Flanagin A, et al. AMA Manual of Style: A Guide for Authors and Editors. 10th ed. New York, NY: Oxford University Press; 2007.

Merriam-Webster's Collegiate Dictionary. 11th ed. Springfield, MA: Merriam-Webster, Inc.; 2007.

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