<p>What is meant by "logical language", is that the language's grammar is engineered so that any statement you make is <em>syntactically</em> unambiguous. Grammatically correct statements only parse one way.</p>

<p>In natural languages, and many constructed languages, the meaning of a statement can be interpreted to be a number of things, depending on context.</p>

<p>An example to given in the "Complete Lojban Language" book (CLL), is the term "Pretty Little Girls’ School". In English, there's no way to tell what this means. Does it mean a school for "pretty little girls", a pretty school for "little girls", or a small school that is pretty and for girls?</p>

<p>Lojban's grammar is such that the relationship between words is unambiguous. The meaning to words themselves doesn't matter all too much to the language's designers, just the relation between those words. As such, ambiguity is still possible, but usually in the form of semantic vagueness.</p>

<p>That said, it's not like there's only one way to say anything. According to the CLL, there are <a href="https://lojban.github.io/cll/5/16/" rel="noreferrer"><strong>Forty</strong> ways</a> to translate the English phrase "Pretty Little Girls' School" into Lojban. Among them, is <code>melbi cmalu nixli ckule</code>, which would be a direct translation of the English phrase, word-for-word, and refer a "school for girls who are beautifully small". Whatever "beautifully small" means.<br>
But if you go through the list of possible interpretations, you'll notice that there are in fact some statements that evaluate to the same meaning, either because that's how the semantics work out, or because the two statements can be logically equivalent. (<code>2 + 2 = 4</code> is equivalent to <code>2 × 2 = 4</code> and <code>2² = 4</code>)</p>

<p>Ultimately, these properties are what make Lojban a tempting tool to use for communicating with AI, who are notoriously bad at working out vague context we use in everyday speech. And it's also why Lojban is called a "Logical Language".</p>

CC BY-SA 4.0
2018-10-09T03:00:50.040Z
Hm, I remember seeing an appendix to one of the old Loglan books that listed seventeen meanings for “pretty little girls' school”.  Now there's forty?  Progress!
Anton Sherwood
CC BY-SA 3.0
2018-02-07T02:02:19.510Z
2018-02-07T02:09:21.443Z
2018-02-07T02:09:21.443Z
TUSF
<p>The syntax of a logical language is amenable to <a href="https://en.wikipedia.org/wiki/Rewriting" rel="nofollow noreferrer">rewriting</a>, which generates a <a href="https://en.wikipedia.org/wiki/Formal_system#Deductive_system" rel="nofollow noreferrer">deductive system</a>, a special case of a formal system. There are two main features of a logical language:</p>
<ul>
<li>Some utterances are provably equivalent to each other</li>
<li>Some utterances provably imply other utterances</li>
</ul>
<p>For the case of Lojban, I maintain <a href="https://mostawesomedude.github.io/brismu/" rel="nofollow noreferrer">brismu</a>, a living collection of rewrite rules and formal proofs.</p>

CC BY-SA 4.0
2023-07-16T15:30:33.683Z
2023-07-16T15:39:37.563Z
2023-07-16T15:39:37.563Z
Corbin
<p>The title says it all. While I have not studied it, I have repeatedly heard that lojban is an especially "logical" language, one that could even be a way to speak a "natural" language to the computer that it can understand.</p>

<p>What feature of lojban (or features) makes this so? Is it just that humans haven't gotten to it yet?</p>

CC BY-SA 3.0
2018-02-07T01:17:10.840Z
Yes - would it remain so pure if a speech community used it like any natural language? I doubt it.
curiousdannii
<lojban><language-structure>
What makes lojban such a "logical" language?
# What makes lojban such a "logical" language?

(Asked by: username_0 on 2018-02-07)

The title says it all. While I have not studied it, I have repeatedly heard that lojban is an especially "logical" language, one that could even be a way to speak a "natural" language to the computer that it can understand.

What feature of lojban (or features) makes this so? Is it just that humans haven't gotten to it yet?

**Tags:** lojban, language-structure

> **Comments:**
> **username_1**: Yes - would it remain so pure if a speech community used it like any natural language? I doubt it.  

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## 2 answers

### Answer by username_2 on 2018-02-07. Score: 13

What is meant by "logical language", is that the language's grammar is engineered so that any statement you make is *syntactically* unambiguous. Grammatically correct statements only parse one way.

In natural languages, and many constructed languages, the meaning of a statement can be interpreted to be a number of things, depending on context.

An example to given in the "Complete Lojban Language" book (CLL), is the term "Pretty Little Girls’ School". In English, there's no way to tell what this means. Does it mean a school for "pretty little girls", a pretty school for "little girls", or a small school that is pretty and for girls?

Lojban's grammar is such that the relationship between words is unambiguous. The meaning to words themselves doesn't matter all too much to the language's designers, just the relation between those words. As such, ambiguity is still possible, but usually in the form of semantic vagueness.

That said, it's not like there's only one way to say anything. According to the CLL, there are [**Forty** ways](https://lojban.github.io/cll/5/16/) to translate the English phrase "Pretty Little Girls' School" into Lojban. Among them, is `melbi cmalu nixli ckule`, which would be a direct translation of the English phrase, word-for-word, and refer a "school for girls who are beautifully small". Whatever "beautifully small" means.  
But if you go through the list of possible interpretations, you'll notice that there are in fact some statements that evaluate to the same meaning, either because that's how the semantics work out, or because the two statements can be logically equivalent. (`2 + 2 = 4` is equivalent to `2 × 2 = 4` and `2² = 4`)

Ultimately, these properties are what make Lojban a tempting tool to use for communicating with AI, who are notoriously bad at working out vague context we use in everyday speech. And it's also why Lojban is called a "Logical Language".

> **Comments:**
> **username_3**: Hm, I remember seeing an appendix to one of the old Loglan books that listed seventeen meanings for “pretty little girls' school”.  Now there's forty?  Progress!  

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### Answer by username_4 on 2023-07-16. Score: 1

The syntax of a logical language is amenable to [rewriting](https://en.wikipedia.org/wiki/Rewriting), which generates a [deductive system](https://en.wikipedia.org/wiki/Formal_system#Deductive_system), a special case of a formal system. There are two main features of a logical language:

* Some utterances are provably equivalent to each other
* Some utterances provably imply other utterances

For the case of Lojban, I maintain [brismu](https://mostawesomedude.github.io/brismu/), a living collection of rewrite rules and formal proofs.


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