Overview
The application of the term to the act appears to arise from the idea that "criminal intercourse with a married woman ... tended to adulterate the issue of an innocent husband ... and to expose him to support and provide for another man's ". Thus, the "purity" of the children of a marriage is corrupted, and the inheritance is altered. The law often uses the word "adulterate" to describe contamination of food and the like.
Three recent studies in the United States, using nationally representative samples, have found that about 10–15% of women and 20–25% of men admitted to having engaged in extramarital sex. Other studies in the US have higher numbers (see United States below).
Read more about this topic: Adultery