Clarify valid uses of 𝕎 as Nothing

1 files changed, 1 insertions, 1 deletions

diff --git a/spec/evaluate.md b/spec/evaluate.md
index 0ad6bf10..90ed32a9 100644
--- a/spec/evaluate.md
+++ b/spec/evaluate.md
@@ -20,7 +20,7 @@ To evaluate a block when enough inputs have been received, first the correct cas
 
 The only remaining step before evaluating the `BODY` is to bind the inputs and other names. Special names are always bound when applicable: `𝕨𝕩𝕤` if arguments are used, `𝕨` if there is a left argument, `𝕗𝕘` if operands are used, and `_𝕣` and `_𝕣_` for modifiers and combinators, respectively. Any names in the header are also bound, allowing multiple assignment for arguments.
 
-If there is no left argument, but the `BODY` contains `𝕨` at the top level, then it is conceptually re-parsed with `𝕨` replaced by `·` to give a monadic version before application; this modifies the syntax tree by replacing some instances of `arg` with `nothing`. However, it also causes an error if, in a function that is called with no left argument, `𝕨` is used as an operand or list element, where `nothing` is not allowed by the grammar. The same effect can also be achieved dynamically by treating `·` as a value and checking for it during execution. If it is used as a left argument, then the function should instead be called with no left argument (and similarly in trains); it it is used as a right argument, then the function and its left argument are evaluated but rather than calling the function `·` is "returned" immediately; and if it is used in another context then it causes an error.
+If there is no left argument, but the `BODY` contains `𝕨` or `𝕎` at the top level, then it is conceptually re-parsed with `𝕨` replaced by `·` to give a monadic version before application; this modifies the syntax tree by replacing some instances of `arg` with `nothing`. However, it also causes an error if, in a function that is called with no left argument, `𝕨` is used as an operand or list element, where `nothing` is not allowed by the grammar. In the case of `𝕎` it's almost always an error, only valid if used alone in a statement or as the left part of a `Fork`. True re-parsing is not required as the same effect can also be achieved dynamically by treating `·` as a value and checking for it during execution. If it's used as a left argument, then the function should instead be called with no left argument (and similarly in trains); if it's used as a right argument, then the function and its left argument are evaluated but rather than calling the function `·` is "returned" immediately; and if it's used in another context then it causes an error.
 
 ### Assignment