In the legal term "null and void," what is the difference between null and void? Why not just use one of the two terms? And can either term be used without the other?
I don't remember how I learned this, and I can't find a reference just now, but the peculiar custom of redundancy in our legal documents dates back to medieval England. The Norman conquest of 1066 put a French-speaking king and nobility in charge of an English-speaking people. The English courts at the time were extremely sensitive to detail and would throw out a petition for something as minor as a misspelling, so getting every detail right was crucial. Thus, lawyers developed a habit of incorporating English synonyms for key French words (or it might have been the reverse; memory fails me on that detail). This is how we get phrases like null and void and cease and desist. Since American law (except in the state of Louisiana) is based on English common law, the U.S. inherited this custom. Over time, I suspect the legal professional largely forgot exactly why it was building all this redundancy into its documents and "decided" it was as a general matter of belt-and-suspenders caution.
EDIT: I finally found a reference of sorts at Wikipedia:
David Crystal (2004) explains a stylistic influence upon English legal language. During the Medieval period lawyers used a mixture of Latin, French and English. To avoid ambiguity lawyers often offered pairs of words from different languages. Sometimes there was little ambiguity to resolve and the pairs merely gave greater emphasis, becoming a stylistic habit. This is a feature of legal style that continues to the present day. Examples of mixed language doublets are: "breaking and entering" (English/French), "fit and proper" (English/French), "lands and tenements" (English/French), "will and testament" (English/Latin). Examples of English-only doublets are: "let and hindrance", "have and hold."
Curious to learn more about Ms. Hess' answer, I undertook a little more research* today...
The history begins, as with so many curiosities in the English language, with the Norman invasion in 1066. At that time, English was the language of the ordinary people, and the law. At first, William the Conqueror interfered little with use of English in official documents, primarily to bolster his claim to the throne, as it was before his reign strongly associated with the crown and kingly continuity. As time went on, however, and as more and more Normans gained positions of prominence in the English court, and were elevated to the nobility, French came to be the spoken language of the upper-class, and Latin, the imported written language of the learned, eventually came to completely replace Old English in legal documents. This continued for some 250 odd years.
By 1275, we find the first statutes written in French, and by 1310 French had overtaken Latin as the language of law. Well, not exactly overtaken; important Latin legal terms, terms of art, were being sprinkled in French language, where needed. We have inherited these terms up to the present day; this is where our civil law gets important concepts like mens rea, habeaus corpus, writs of mandamus, and a million other terms. Still, Law French was the language that lawyers communicated with each other in, and lawyers continued to develop their the profession with it, creating ever new terms of art when trying, pleading, and judging cases. Things continued in this way for a 100 more years.
Curiously, just as French was just reaching its supremacy as official written language of the Law, it was dying out as a spoken language among the nobility. Increasingly, they were speaking a bastardized pidgin of English and French called Anglo-Norman, and by 1400, Anglo-Norman had nearly died out even amongst the royal household in favor of English. Henry V broke things off completely with his Norman heritage after famously going to war with France in the Hundreds Years' War. English, with modifications, had now become the language of all the English people.
Well, mostly. Law French was still the obscure, technical language of the legal profession, and it was contributing many terms of art of its own, particularly in property law: this is where property law jargon like estoppel, estate, and esquire come from. However, even the lawyers eventually lost control of a tongue they didn't speak, and legalese became a complex argot of Law Latin and Law French terms swimming in a sea of ordinary English.
A conundrum. By 1362, we have evidence that the courts were becoming recognizant of this troublesome state of affairs, as a Statute of Pleading was enacted "condemning French as 'much unknown in said Realm'" and requiring that "all pleas be 'pleaded, shewed, defended, answered, and debated, and judged in the English tongue.'" Ironically enough, the Statute itself was written in Law French, and it was not till 200 years later, when the vocabulary of Law French had shrunk to about 1000 words, that English became the dominant language of the law.
Still, all those terms of art couldn't be simply abandoned. So lawyers of the day simply did the next best thing: they imported synonyms acknowledged as "English" to accompany those technical terms, to give the "synonyms" independent legal weight in documents, and eventually, the combination of the two became phrases with inertia of their own. Such as:
breaking and entering
fit and proper
will and testament
free and clear
acknowledge and confess
law and order
to have and to hold
(English terms are italicized.)
"But Billare!" "Isn't your answer supposed to be talking about null and void?" "And, if I'm not mistaken, doesn't null come from the Latin nullus, meaning 'not any, none,' and doesn't void come from the Latin vocivus, meaning 'unoccupied, vacant'"? "Where's the Old English term there?!"
Ah, yes. The punchline. Null and void became a phrase of their own because the two synonyms from Latin were imported at different times into "ordinary" English. I quote from David Melinkoff's The Language of Law:
Early in the reign of Elizabeth I, null – with a long life as a negative in law French and in Latin – became an English synonym for the law's use of void. Another hundred years, and null and void were a team, null taking the place of other explanatory nothingness (no value, no effect) that had often accompanied void. The combination stuck despite frowns in and out of the law.
So it follows the same rule. Null and void is a semantically redundant phrase because it was formed as a compromised term of art, and has continued in this way for a long, long time.
*: All acknowledgments and quotes go to this most excellent book, Legal Language, by a certain Peter Tiersma, where I found basically most of this research. Do read it if you're interested in more.
F'x's answer is completely correct with regards to the usage of the legal term "null and void": Both refer to the same meaning of invalidity. As best as I can tell, "void" is the most appropriate of the two to use if you want to trim your word count.
For everything else, however, the terms do have different meanings. Null means "empty" or "insignificant" and is used a placeholder for "nothing." It holds a special meaning for set notation and programming.
A void can mean an emptiness or chasm ("Don't step into the void.") and has been used to describe the bleakness of outer space. It presents the idea of emptiness in the form of what happens when you dig out a hole: The hole's substance is now a "void."
The difference between null and void as term for nothing stems from their place in physical space. A void is nothing but takes up space; null is nothing at all. In other words, you could measure a void but null offers nothing to measure.
Void also means canceled or deleted and, again, programming has a special meaning for the term void. Here are a handful of usages for both terms:
(mathematics) The empty set is always a null set but a null set is not necessarily the empty set.
(programming) The program is choking on a null pointer exception.
This deal has rendered our profits null.
He is void of remorse.
This check is void.
This offer is void where prohibited.
They were lost to the void.
The planet was replaced with void.
(programming) This function returns
void. / This is a
To summarize: The legal term of "null and void" means the same as "void." The two words have plenty of varied uses in other fields with extremely subtle differences that are important to the members of those fields. Browsing the Wikipedia disambgiuation pages for null and void is a good way to spot the number of differences between the words.
It is common in legal terminology to throw in extra words in an attempt to cover as many cases as possible. For example, you always hear heirs and assigns in contracts concerning real estate:
An occupancy agreement must provide that it's binding on heirs, assigns, executors, administrators, and successors.
This is the legalese way of making sure all bases are covered. By saying null and void the originators of the usage were no doubt attempting to forestall any argument that null or void taken singly did not mean invalid in quite the right way, or was insufficient by itself to mean that, and that therefore a case could be made that a contract was still in effect. A lot of litigation is predicated on arguing very fine points, and these include the meaning of words that may seem obvious to you and me.
If one voids a voidable contract, the contract is not null. Where a distinction is drawn, a contract is 'void' if it does not bind the parties. A contract is 'null' if it has no effects whatsoever.
For example, say Jeff steals a widget from Mark and sells it to Jack. This contract is void because Jeff has attempted to transfer an ownership he doesn't have. But it is not null because it will affect what happens if Mark sues Jack (to get his widget back) or Jack sues Jeff (to get his money back).
The terms are sometimes used interchangeably. But strictly speaking, one who avoids a contract has voided it. They generally do not nullify it. A divorce voids a marriage (so that the marriage no longer continues to exist), but only an anulment makes it null (so it has no consequences).
The meaning, as applied to contracts, is similar but not identical.
One refers to a contract that potentially was effective, but is made non-binding by action of some party.
The other means the contract was defective and could never have legal effect.
I think the first case is void, and the second is null, but IANAL.
(For example, if a party backs out of a sale before it is finalized, it - the contract of sale - is said to be "voided", and neither party is obligated by it. A sale following false advertising is "voidable" - one party is innocent, and at their option the contract will either be enforced or not. Sale of property that the seller did not have title to is "null" -- the parties cannot make it binding even if all are aware of the fraud.)
In general no two words are perfect synonyms, and no word from another language or dialect is a perfect substitute. When words are used in a technical sense, the words in the special register (in this case legalese) specialize away from the usage in the general language, although generally some of the new import leaks back.
David Schwartz and Ben Voigt illustrate that there is a difference between null and void in the context of contract law, and as it pertains to general language this comes back to an extent, with null (and the verb annul) looking to the past and meaning "as if it had never been" and void (and the verb void, and the related avoid) looking to the future "to ensure it has no further influence".
In law, there is an aim to ensure absolute clarity, broadest coverage, and minimum of misunderstanding and absence of loopholes as Robusto points out. Using multiple near synonyms makes progress to this and combines all the shades of meaning, covering loopholes that any one alone might leave. The situation of transitioning between languages or systems, also specifically warrants this parallel transitional language, as Kelly Hess and Billare so well describe.
This parallelism of near synonyms is not only something that occurs in legalese, and not only something that we do with individual words. For instance, in poetry layers of meaning or example reinforce the desired effect, including sometimes using (double) negative language. Different ways of negating this (back to null and void) can emphasize different types of oppositeness, and the double negations are thus not synonyms either. Hebrew poetry (see Psalms) is especially known for its paired parallels, or even its threes, often with afterthought fourth (see Proverbs 30). If we are making a point, even in modern English, we like to be able to count off at least two or three reasons or examples on our fingers, as "two or three witnesses" rather than an anomaly. In a lecture, I will try to explain anything at least three different ways to reach all parts of the audience - including a high level theoretical explanation, an exposition of insightful intuition, and a common exemplar (often in the reverse order).