The following cmavo are discussed in this section:
ju'u 
VUhU 
to the base 
dau 
PA 
hex digit A = 10 
fei 
PA 
hex digit B = 11 
gai 
PA 
hex digit C = 12 
jau 
PA 
hex digit D = 13 
rei 
PA 
hex digit E = 14 
vai 
PA 
hex digit F = 15 
pi'e 
PA 
compound base point 
In normal contexts, Lojban assumes that all numbers are expressed in the decimal (base 10) system. However, other bases are possible, and may be appropriate in particular circumstances.
To specify a number in a particular base, the VUhU operator ju'u is suitable:
Here, the final pa no is assumed to be base 10, as usual; so is the base specification. (The base may also be changed permanently by a metalinguistic specification; no standard way of doing so has as yet been worked out.)
Lojban has digits for representing bases up to 16, because 16 is a base often used in computer applications. In English, it is customary to use the letters AF as the base 16 digits equivalent to the numbers ten through fifteen. In Lojban, this ambiguity is avoided:
Note the pattern in the cmavo: the diphthongs .au , .ei , .ai are used twice in the same order. The digits for A to D use consonants different from those used in the decimal digit cmavo; E and F unfortunately overlap 2 and 4 – there was simply not enough available cmavo space to make a full differentiation possible. The cmavo are also in alphabetical order.
The base point pi is used in nondecimal bases just as in base 10:
Since ju'u is an operator of selma'o VUhU, it is grammatical to use any operand as the left argument. Semantically, however, it is undefined to use anything but a numeral string on the left. The reason for making ju'u an operator is to allow reference to a base which is not a constant.
There are some numerical values that require a “base” that varies from digit to digit. For example, times represented in hours, minutes, and seconds have, in effect, three “digits” : the first is base 24, the second and third are base 60. To express such numbers, the compound base separator pi'e is used:
Each digit sequence separated by instances of pi'e is expressed in decimal notation, but the number as a whole is not decimal and can only be added and subtracted by special rules:
li  ci  pi'e  rere  pi'e  vono  su'i  pi'e  ci  pi'e  cici 
Thenumber  3  :  22  :  40  plus  :  3  :  33 
du  li  ci  pi'e  rexa  pi'e  paci  
equals  thenumber  3  :  26  :  13.  
3:22:40 + 0:3:33 = 3:26:13

Of course, only context tells you that the first part of the numbers in Example 18.74 and Example 18.75 is hours, the second minutes, and the third seconds.
The same mechanism using pi'e can be used to express numbers which have a base larger than 16. For example, base20 Mayan mathematics might use digits from no to paso , each separated by pi'e :
Carefully note the difference between:
which is equal to ten, and:
which is equal to twenty.
Both pi and pi'e can be used to express largebase fractions:
li  pa  pi'e  vo  pi  ze  ju'u  reno 
Thenumber  1  ;  4  .  7  base  20 
du  li  revo  pi  cimu 
equals  thenumber  24  .  35 
pi'e is also used where the base of each digit is vague, as in the numbering of the examples in this chapter:
dei  jufra  panopi'epapamoi 
Thisutterance  isasentencetypeof  10;11ththing. 
This is Sentence 10.11. 