The following cmavo are discussed in this section:
.abu 
BY 
letter “a” 
by 
BY 
letter “b” 
cy 
BY 
letter “c” 
fe'a 
VUhU 
nth root of (default square root) 
lo'o 
LOhO 
terminator for LI 
As befits a logical language, Lojban has extensive provision for logical connectives within both operators and operands. Full details on logical and nonlogical connectives are provided in Chapter 14. Operands are connected in afterthought with selma'o A and in forethought with selma'o GA, just like sumti. Operators are connected in afterthought with selma'o JA and in forethought with selma'o GUhA, just like tanru components. This parallelism is no accident.
In addition, A+BO and A+KE constructs are allowed for grouping logically connected operands, and ke … ke'e is allowed for grouping logically connected operators, although there are no analogues of tanru among the operators.
Despite the large number of rules required to support this feature, it is of relatively minor importance in the mekso scheme of things. Example 18.114 exhibits afterthought logical connection between operands:
Example 18.115 is equivalent in meaning, but uses forethought connection:
Note that the mekso here are being used as quantifiers. Lojban requires that any mekso other than a simple number be enclosed in parentheses when used as a quantifier. This rule prevents ambiguities that do not exist when using li.
By the way, li has an elidable terminator, lo'o , which is needed when a li sumti is followed by a logical connective that could seem to be within the mekso. For example:
li  re  su'i  re  du 
Thenumber  two  plus  two  equals 
li  vo  lo'o  .onai  lo  nalseldjuno  namcu 
thenumber  four  orelse  a  nonknown  number. 
Omitting the lo'o would cause the parser to assume that another operand followed the .onai and reject lo as an invalid operand.
Simple examples of logical connection between operators are hard to come by. A contrived example is:
li  re  su'i  je  pi'i  re  du  li  vo  
Thenumber  two  plus  and  times  two  equals  thenumber  four.  
2 + 2 = 4 and 2 × 2 = 4.

The forethoughtconnection form of Example 18.117 is:
li  re  ge  su'i  gi  pi'i  re  du  li  vo  
thenumber  two  both  plus  and  times  two  equals  thenumber  four.  
Both 2 + 2 = 4 and 2 × 2 = 4.

Here is a classic example of operand logical connection:
go  li  .abu  bi'epi'i  vei  xy.  te'a  re  ve'o  su'i 
Ifandonlyif  thenumber  “a”  times  (  “x”  power  two  )  plus 
by.  bi'epi'i  xy.  su'i  cy.  du  li  no 
“b”  times  “x”  plus  “c”  equals  thenumber  zero 
gi  li  xy.  du  li  vei  va'a  by.  ku'e 
then  thenumber  x  equals  thenumber  [  thenegationof(  b  ) 
su'i  ja  vu'u  fe'a 
plus  or  minus  therootof 
vei  by.  bi'ete'a  re  vu'u  vo  bi'epi'i  .abu  bi'epi'i  cy. 
(  “b”  power  2  minus  four  times  “a”  times  “c” 
ve'o  [ku'e]  ve'o  fe'i  re  bi'epi'i  .abu  
)  ]  dividedby  two  times  “a”  
$$Iffa{x}^{2}+bx+c=0,\; thenx=\frac{b\pm \sqrt{{b}^{2}4ac}}{2a}$$

Note the mixture of styles in Example 18.119 : the negation of b and the square root are represented by forethought and most of the operator precedence by prefixed bi'e , but explicit parentheses had to be added to group the numerator properly. In addition, the square root parentheses cannot be removed here in favor of simple fe'a and ku'e bracketing, because infix operators are present in the operand. Getting Example 18.119 to parse perfectly using the current parser took several tries: a more relaxed style would dispense with most of the bi'e cmavo and just let the standard precedence rules be understood.
Nonlogical connection with JOI and BIhI is also permitted between operands and between operators. One use for this construct is to connect operands with bi'o to create intervals:
li  no  ga'o  bi'o  ke'i  pa  
thenumber  zero  (inclusive)  fromto  (exclusive)  one  
[0,1)

the numbers from zero to one, including zero but not including one 
Intervals defined by a midpoint and range rather than beginning and end points can be expressed by mi'i :
which expresses the same interval as Example 18.120. Note that the ga'o and ke'i still refer to the endpoints, although these are now implied rather than expressed. Another way of expressing the same thing:
Here we have the sum of a number and an interval, which produces another interval centered on the number. As Example 18.122 shows, nonlogical (or logical) connection of operands has higher precedence than any mekso operator.
You can also combine two operands with ce'o , the sequence connective of selma'o JOI, to make a compound subscript: