Four quartiles?

Given that only three quartiles are defined, the middle one also known as the median (see The International Statistical Institute. The Oxford Dictionary of Statistical Terms. Oxford University Press, New York 2003), it is surprisingly common to see results presented with four quartiles. The explanation is, of course, that the term is misunderstood. The misunderstanding is actually so common that the Merriam-Webster dictionary states that the four quartiles are the same as the four quarts defined by the three quartiles. Confusing? While the exact definition may be of minor importance when writing fiction, avoiding misunderstandings is a crucial part of scientific writing. Stick to the statistical definition of statistical terms.