In law, a dictum
is a statement in a judge
's opinion which is extraneous to the holding
in the case. Most major court decisions are chock full of dicta, since judges tend to explain their reasoning in nauseating detail whenever their thinking process might be checked in the future.
The most important thing to know about dicta is that they do not constitute precedent. In common law countries, such as the U.S., Canada, and Britain, judges' past holdings usually have to be followed by courts within their jurisdiction. However, dicta do not get this sort of treatment: they can be cited in other cases for persuasive purposes (especially if they come from a prominent court and/or judge), but they have no authority as law.
For example, let's say that E2 has a judicial system based on common law. dannye, the plucky State Attorney, decides to charge J. Random Noder for making a node called "Harry S Truman" in violation of the Pick Titles Carefully statute, paragraph 4 ("Use a period after the middle initial if the person's middle initial is usually mentioned.") The case ends up in the Everything2 Superior Court, where Judge dem bones rules:
Everything2 v. Noder
Cite as: 19 Ev.2d 183 (2004)
The state brings charges against J. Random Noder for violating Pick Titles Carefully, paragraph 4.
As a general principle, the purpose of a node title is so that someone can find the node your writeup is in later. By "someone" we mean the E2 search engine. The words in node titles are the keys to the search engine.
In the case at hand, the title "Harry S Truman" is widely considered to be correct form for stating the full name of the U.S. president in question. It is therefore obvious that the node is citing Truman's full name, and not merely his middle initial. Because the node title has used proper convention, we see no basis for the state's inquest, and thereby rule that no charges may be pressed.
Note that the second paragraph of bones's opinion has next to nothing to do with his final verdict. Now, let's say that another prosecutor, liveforever, decides to strike down another "troublesome" title. In his brief, he writes:
This court has already ruled that the purpose of a node title is to aid the search engine. Everything2 v. Noder, 19 Ev.2d 183 (2004).
liveforever isn't entirely correct on this one. The ruling in the case was that a middle name resembling a middle initial does not need to have a period after it. (A good noding lawyer could probably generalize further*.) The entire search engine statement was merely a dictum. Since it wasn't actually part of the ruling on the case, liveforever can't cite it as precedent. However, he could say:
Judge dem bones has stated, in a dictum to a prominent titling case, that the purpose of a node title is to aid the search engine. Everything2 v. Noder, 19 Ev.2d 183 (2004).
In this case, he's merely pointing to it as the opinion of a prominent Everythingian, rather than an actual law.
*boy, that invited some responses. haze, a real lawyer, puts it thusly: "A period need not follow when the middle initial without the period is 'widely considered to be the correct form for stating the full name in question.' 19 Ev.2d 183 (2004) (Bones, J.)."