http://originalintent.org/edu/thelaw.php#language

The Language of Law

One of the greatest stumbling blocks for the American public in understanding the laws their representatives enact is that laws use words in a different manner than we do in common speech.

There are two kinds of language that are primarily used in law - one is "words" (just as we use in common speech) and the other is "terms" (which can be substantially different than we use in common speech).

"Words" are just that - words. They are presumed to be used in their ordinary manner and they are subject to the "plain meaning rule" when interpreting a statute. Their meaning must be sought through the common English dictionaries of the era in which the statute was written. In the absence of any clear contrary intent by the legislature, the meaning found in these dictionaries is the sole meaning that must be given to the word.

"Terms" are another matter. Terms appear no different, to the layperson, than words. The difference is that terms are not subject to the "plain meaning rule" because the legislature has provided its own definition for the term being used. Where the legislature has provided its own definition, the ordinary English dictionary must be thrown out the window; the definition given to the term by the legislature controls the meaning completely.

The meanings of terms can be identified by seeking out the "definitions" section applicable the text that you are reading. Unfortunately, this may not always be as straight forward a proposition as one might imagine.

Most codes provide a section that gives definitions that are generally applicable throughout the entire code, however any of the definitions given for the entire code are subject to be redefined in any given subtitle, chapter, section, subsection, or clause. Any time a term is redefined for a specific subtitle, chapter, section, subsection, or clause, that redefinition of the term takes precedent (within that subtitle, chapter, section, subsection, or clause) over the general definition provided for the entire code. Of course, to make matters more confusing, any time a term is redefined for use in a subtitle, chapter, section, subsection, or clause, it can be redefined again and again as you move from subtitle to chapter; chapter to chapter; chapter to section; section to section; section to clause, etc. In other words, you always have to be on your toes and make sure you know the definitions that apply to the exact text your reading!

Here is an example. 26 USC 7701 contains definitions that applicable for the entire Internal Revenue Code. Section 7701(a)(20) defined "employee":

For the purpose of applying the provisions of section 79 with respect to group-term life insurance purchased for employees, for the purpose of applying the provisions of sections 104, 105, and 106 with respect to accident and health insurance or accident and health plans, and for the purpose of applying the provisions of subtitle A with respect to contributions to or under a stock bonus, pension, profit-sharing, or annuity plan, and with respect to distributions under such a plan, or by a trust forming part of such a plan, and for purposes of applying section 125 with respect to cafeteria plans, the term ''employee'' shall include a full-time life insurance salesman who is considered an employee for the purpose of chapter 21, or in the case of services performed before January 1, 1951, who would be considered an employee if his services were performed during 1951.

The term is redefined for use in chapter 24 of the Code: (26 USC 3401(c))

For purposes of this chapter, the term ''employee'' includes an officer, employee, or elected official of the United States, a State, or any political subdivision thereof, or the District of Columbia, or any agency or instrumentality of any one or more of the foregoing. The term ''employee'' also includes an officer of a corporation.

As you can see the terms are defined very differently. The title-wide definition addresses insurance salesmen, while the definition for chapter 24 addresses only government workers under the direct or indirect authority of the federal government. [The corporation that is mentioned is a corporation wholly owned by the federal government.]

Words of Art

Although "Words of Art" are often placed (by the layperson) in the same category as "terms", they are not the same thing. Words of Art are words or phrases that are particular to specific technologies, sciences, arts, professions, etc., and generally do not have the same meaning, or any meaning at all, outside their own field. One example of this is the medical word, "orthopod". The word, "orthopod" is generally used within the medical community to indicate a person who has surgical training and experience in arthroscopy. Outside the medical field, "orthopod" has no meaning whatsoever. While "terms" are often used by politicians and lawyers to mask the true intentions or application of legislation from the general public (especially in tax law), Words of Art are a proper and necessary parts of effective communication in the legal arena.