The following cmavo are discussed in this section:
ci'i PA infinity
ka'o PA imaginary i, sqrt(-1)
pai PA π, pi (approx 3.14159...)
te'o PA exponential e (approx 2.71828...)
fi'u PA golden ratio, Φ, phi, (1 + sqrt(5))/2 (approx. 1.61803...)
The last cmavo is the same as the fraction sign cmavo: a fraction sign with neither numerator nor denominator represents the golden ratio.
Numbers can have any of these digit, punctuation, and special-number cmavo of Sections 2, 3, and 4 in any combination:
4.1) ma'u ci'i
+∞
4.2) ci ka'o re
3i2 (a complex number equivalent to “3 + 2i”)
Note that “ka'o” is both a special number (meaning “i”) and a number punctuation mark (separating the real and the imaginary parts of a complex number).
4.3) ci'i no
infinity zero
ℵ0 (a transfinite cardinal)
The special numbers “pai” and “te'o” are mathematically important, which is why they are given their own cmavo:
4.4) pai
pi, π
4.5) te'o
e
However, many combinations are as yet undefined:
4.6) pa pi re pi ci
1.2.3
4.7) pa ni'u re
1 negative-sign 2
Example 4.7 is not “1 minus 2”, which is represented by a different cmavo sequence altogether. It is a single number which has not been assigned a meaning. There are many such numbers which have no well-defined meaning; they may be used for experimental purposes or for future expansion of the Lojban number system.
It is possible, of course, that some of these “oddities” do have a meaningful use in some restricted area of mathematics. A mathematician appropriating these structures for specialized use needs to consider whether some other branch of mathematics would use the structure differently.
More information on numbers may be found in Sections 8 to 12.