Lojban (/LOZH-bahn/) is a constructed language derived from loglan. It is based on the principles of logic and has an unambiguos machine parsable grammar. Is is designed to be culturally neutral. One of the orginal goals was to design a language that could be used to test the Sapir-Whorf hypothesis.

The Lojban language was first called loglan by Dr. James Cooke Brown. He started the development in 1955 but in 1987, The Logical Language Group took over it and they never stopped the work.
Lojban is culturally neutral and regular. That means there are no dumb exceptions (like in french).
It has something like 1300 root words that can be combined to form millions of words without problem.

An example of the language :
la lojban. po'u le logji bangu
means 'Lojban - the Logical Language'.

The word "Lojban" means "logic-language", but that only means that it is based on first order logic, and has a grammar based on predicates. It does not imply that the language is more rational than others.

In fact, the Lojban vocabulary has some rather odd quirks. For instance, all words that refer to animals, are based on the same place structure pattern. Except three animals (guess which!): tigers, sheep, and human beings.

There has been a rather lengthy discussion on their mailing list, where some people argued that the word know should not be a concept of its own, as it has two meanings collapsed into one: "x₁ knows x₂" is equivalent in meaning to "x₁ is convinced that x₂ is true AND x₂ is actually true".

Lojban experts have also recently concluded that the word botpi (bottle) should only be used to refer to bottles that contain something.

arj's claims, while true, don't actually say anything about how logical lojban is or is not.

The sheep/tiger thing is kinda stupid. It's too late to change the dictionary. However, the extra places used by sheep and tigers are places that aren't used by other animals, so you could just as easily apply the generic animal place structure to them.

Is something illogical about analyzing the meaning of the word know? The word djuno is still part of Lojban, despite that some people think it is redundant.

It is misleading to describe the word botpi that way. botpi, like every other Lojban root word, is a predicate which can also be used as a noun, adjective, or adverb. You can think of its primary meaning as a verb - "This is a bottle of water" could be said, more awkwardly (in English), "this thing bottles water". If something doesn't bottle anything, then it would be false to say that it currently does botpi. However, if you leave off the tense, it is not false - "this is something that bottles" (ti botpi) can be true if it ever has bottled or if it is expected to.

The Lojban word for a bottle, whether or not it bottles anything, is botytai (bottling-form), not botpi (that which bottles).

Finally, arj made the mistake of listening to the Lojban mailing list, which very frequently ends up in confusing metalinguistic arguments. This is illustrated by a joke which once had its own node:

How many Lojbanists does it take to change a broken lightbulb?
Two: one to decide what to change it into, and another to figure out what kind of bulb would emit broken light.