I suppose in a sense all languages are constructed (they didn't fall from
trees), but the term generally refers to languages that were consciously
invented, particularly by one person or a small group, as opposed to
developing naturally in the usual way. A well-chosen term for this is
Planned Languages, which I think works well, but usually you just
constructed language or
Constructed languages are created for various purposes, and maybe I'll
treat them separately on separate pages as this section evolves. The
classic motivation is an international language, one that will somehow
facilitate worldwide communication and level the linguistic playing field.
These are the
IALs, the International Auxiliary Languages (sometimes
also called auxlangs). And that
includes probably the largest and best-known constructed language of them
all, Esperanto. I worked with Esperanto for a while, and it may even have
been my start into constructed languages (I remember seeing an article
about it, including some actually written in the language, in
Time magazine in 1987, for the 100th anniversary of Esperanto,
which was first published in 1887). I looked up stuff on the language in
college and started participating on soc.culture.esperanto (this was back
when netnews was still worthwhile).
Back then I was already interested enough in conlangs that my friend Jerry Altzman and I ran a service called the “Planned Languages Server.” It was a sort of file-server by email, which meant you would email requests for files to it and it would email the file back to you. Something that today would surely be done by a simple web page, but this was before the web.
I've pretty much given up on the idea of an auxlang. For one thing, even if it were adopted, it wouldn't result in instant love and harmony and world peace, as auxlang proponents often seem to think. Most wars are fought between people who understand each other quite well. And there's so much acrimony about auxlangs: if you have this feature, it's a disaster; you mustn't structure it that way, blah blah. Back when I was on the conlang mailing list there were such horrible fights about it. Eventually a special list for auxlangs was formed. Still, this doesn't mean I don't like auxlangs as languages and as conlangs. But the concept of making or advocating an auxlang doesn't do it for me.
Other constructed languages have other goals. Sometimes it's an
experiment, like Lojban, which is studying the interaction of language and
logic and how people adapt to a logical language (among other things). Or
Láadan, designed to be a language for women. But
often languages are constructed as a sort of art form. This includes
languages that were made to be a part of some larger work of fiction, such
as Klingon and to some extent J.R.R. Tolkien's languages (I say
some extent because these languages were
not constructed in order to flesh out Middle-Earth, but rather
some of the motivation for writing down stories of Middle-Earth was to give
background for the languages). And some languages are there just to be
themselves, as works of art on their own.
Yf Rgalin is my own meager
contribution to this genre, or would be if I started looking at it again
and blew the dust off and actually worked on it.
You can find more conlangs than
you'll know what to do with, of all sorts, at Jeffrey Henning's LangMaker site.
I've done a lot of work with Lojban, though perhaps not as much as I'd like. It's probably my favorite conlang all around. It's got a lot of confusing stuff, but when it comes down to it, there is always an absolutely clear way of saying what you want (though it may be long). And thinking in Lojban can help you settle in your own mind what it is you mean.
Of course, there's Klingon. I'm the Assistant Director for the Klingon Language Institute, so, yes, I've been involved with that a lot. And that's the one that tends to get the most recognition, because everyone knows about Star Trek—and that's okay too. No, it's not silly or stupid, and no, it isn't only for geeks who have no life and can't get dates. It is an interesting language in its own right, with an unusual syntax and a distinctive world-view, which is what makes any conlang fun.
There are more examples, even if you only count the ones I've studied. Maybe I'll write more about them as stuff about the other ones gets moved onto their own pages.