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Monad and dyad definition

As discussed in the earlier section on ambivalence, all verbs had two definitions, a monad and a dyad. You have defined only a monad for centigrade. What about the dyad?
   23 centigrade 32
|domain error
|   23     centigrade 32
Since you didn't provide a dyad definition, it is empty and this is treated as if the dyad had no arguments in its domain, and any arguments you give will cause a domain error.

Let's examine some simple examples of defining dyadic, monadic, and both cases.
   monadminus =. 3 : 0
- y
)
   monadminus 5
_5
   5 monadminus 3
|domain error
|   5     monadminus 3
The above defines the monad of the verb named monadminus. Applying it monadically works and applying it dyadically fails.

In one-line definitions like this you can take a shortcut and make the definition on a single line and avoid entering the special input mode that needs to be ended with the ). The following is an equivalent way of doing the above definition:
   monadminus =. 3 : '- y'
The string contains the single line that makes up the definition. It is provided directly as the right argument of : instead of the 0 used earlier.

So far you have defined just the monadic case of a verb. You can also define a verb with just a dyadic definition. Instead of 3 as the left argument to : use a 4 to define the dyadic case.
   dyadminus =. 4 : 'x - y'
   5 dyadminus 3
2
   dyadminus 5
|domain error
|       dyadminus 5
In the monad case the y name is the right argument and in the dyad case x is the left argument and y is the right.

What if you want to define both cases of a verb? 
   minus =. 3 : 0
- y
:
x - y
)
The : by itself on a line separates the monad and dyad definitions.
   3 minus 5
_2
   5 minus 3
2
   minus 5
_5
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