diff --git a/src/Driver.mli b/src/Driver.mli
index 1d8c654c8c0780ee4193001f489bb9e61b0647c2..9da0d3749ee8a296a234787362563774eae052fc 100644
--- a/src/Driver.mli
+++ b/src/Driver.mli
@@ -2,4 +2,4 @@
    which could be produced by either ocamlyacc or Menhir. *)
 
 val grammar :
-  (Lexing.lexbuf  -> Parser.token) -> Lexing.lexbuf -> Syntax.grammar
+  (Lexing.lexbuf  -> Parser.token) -> Lexing.lexbuf -> Syntax.partial_grammar
diff --git a/src/fancy-parser.mly b/src/fancy-parser.mly
index 2cd866f6ed19fb74c2470aa9e390c1837287d3e2..854c21292abc1d99247ad51dd0cdc136865990de 100644
--- a/src/fancy-parser.mly
+++ b/src/fancy-parser.mly
@@ -29,7 +29,7 @@ open Positions
 /* ------------------------------------------------------------------------- */
 /* Start symbol. */
 
-%start <Syntax.grammar> grammar
+%start <Syntax.partial_grammar> grammar
 
 /* ------------------------------------------------------------------------- */
 /* Priorities. */
diff --git a/src/internalSyntax.mli b/src/internalSyntax.mli
deleted file mode 100644
index bb3ce8810b47ab00c4b1aa38f6d48e59a0443fe5..0000000000000000000000000000000000000000
--- a/src/internalSyntax.mli
+++ /dev/null
@@ -1,11 +0,0 @@
-type grammar =
-    {
-      p_preludes           : Stretch.t list;
-      p_postludes          : Syntax.trailer list;
-      p_parameters         : Stretch.t list;
-      p_start_symbols      : Positions.t StringMap.t;
-      p_types              : (Syntax.parameter * Stretch.ocamltype Positions.located) list;
-      p_tokens             : Syntax.token_properties StringMap.t;
-      p_rules              : Syntax.parameterized_rule StringMap.t;
-      p_on_error_reduce    : Syntax.parameter list;
-    }
diff --git a/src/parameterizedGrammar.ml b/src/parameterizedGrammar.ml
index 213bea2bdcf228b8b9f676a826f80ce89e467228..7a036a868ddf45b0d9efb4f4e03f865646e6ee57 100644
--- a/src/parameterizedGrammar.ml
+++ b/src/parameterizedGrammar.ml
@@ -1,7 +1,6 @@
 open Positions
 open Syntax
 open UnparameterizedSyntax
-open InternalSyntax
 open Misc
 
 (* Inference for non terminals. *)
@@ -249,7 +248,7 @@ let rec parameter_type env = function
            [Star] otherwise it is the flexible variable. *)
         star_variable
 
-let check_grammar p_grammar =
+let check_grammar (p_grammar : Syntax.grammar) =
   (* [n] is the grammar size. *)
   let n        = StringMap.cardinal p_grammar.p_rules in
 
diff --git a/src/parameterizedGrammar.mli b/src/parameterizedGrammar.mli
index d43fcc11a7d8360b05a30ca418351100e31cfb3f..3a8580859e05c09978fc9c6c7f36e980f57a33ed 100644
--- a/src/parameterizedGrammar.mli
+++ b/src/parameterizedGrammar.mli
@@ -10,6 +10,4 @@
    sanitized via [Misc.normalize] when printed in a context where a
    valid identifier is expected. *)
 
-val expand : InternalSyntax.grammar -> UnparameterizedSyntax.grammar
-
-
+val expand : Syntax.grammar -> UnparameterizedSyntax.grammar
diff --git a/src/partialGrammar.ml b/src/partialGrammar.ml
index e5c3f475b58d8240bac53aa4955223c8061e49fa..02605ffea61df502fbf11be2cd661906320cd5b3 100644
--- a/src/partialGrammar.ml
+++ b/src/partialGrammar.ml
@@ -1,6 +1,5 @@
 open Misc
 open Syntax
-open InternalSyntax
 open Positions
 
 (* ------------------------------------------------------------------------- *)
@@ -432,7 +431,7 @@ let iter_on_only_used_symbols f t =
        | _ -> ())
     t
 
-let symbols_of grammar (pgrammar : Syntax.grammar) =
+let symbols_of grammar (pgrammar : Syntax.partial_grammar) =
   let tokens = grammar.p_tokens in
   let symbols_of_rule symbols prule =
     let rec store_except_rule_parameters =
diff --git a/src/partialGrammar.mli b/src/partialGrammar.mli
index a5a9adcdbe61c882cd115e099379a0d5c8898b32..0ee56580b6db35ace54e44a0d87e5a9c469473fa 100644
--- a/src/partialGrammar.mli
+++ b/src/partialGrammar.mli
@@ -1,2 +1,4 @@
+open Syntax
+
 val join_partial_grammars :
-  Syntax.grammar list -> InternalSyntax.grammar
+  partial_grammar list -> grammar
diff --git a/src/syntax.mli b/src/syntax.mli
index 7ddcbdb5698cdf97e3ec179be4ecb14488c4ad96..783e9c2c73817ea3831be32b33d3a3bcfbde1a62 100644
--- a/src/syntax.mli
+++ b/src/syntax.mli
@@ -1,3 +1,13 @@
+(* The type [partial_grammar] describes the abstract syntax that is produced
+   by the parsers (yacc-parser and fancy-parser).
+
+   The type [grammar] describes the abstract syntax that is obtained after one
+   or more partial grammars are joined (see [PartialGrammar]). It differs in
+   that declarations are organized in a more useful way and a number of
+   well-formedness checks have been performed. *)
+
+(* ------------------------------------------------------------------------ *)
+
 (* Terminals and nonterminal symbols are strings. Identifiers
    (which are used to refer to a symbol's semantic value) are
    strings. A file name is a string. *)
@@ -17,16 +27,24 @@ type identifier =
 type filename =
     string
 
+(* ------------------------------------------------------------------------ *)
+
 (* A trailer is a source file fragment. *)
 
 type trailer =
     Stretch.t
 
+(* ------------------------------------------------------------------------ *)
+
 (* OCaml semantic actions are represented as stretches. *)
 
 type action =
     Action.t
 
+(* ------------------------------------------------------------------------ *)
+
+(* Information about tokens. *)
+
 type token_associativity =
     LeftAssoc
   | RightAssoc
@@ -52,6 +70,8 @@ type token_properties =
       mutable  tk_is_declared   : bool;
     }
 
+(* ------------------------------------------------------------------------ *)
+
 type parameter =
   | ParameterVar of symbol Positions.located
   | ParameterApp of symbol Positions.located * parameters
@@ -123,10 +143,22 @@ type parameterized_rule =
       pr_branches          : parameterized_branch list;
     }
 
-type grammar =
+type partial_grammar =
     {
       pg_filename          : filename;
       pg_declarations      : declaration Positions.located list;
       pg_rules             : parameterized_rule list;
       pg_trailer           : trailer option;
     }
+
+type grammar =
+    {
+      p_preludes           : Stretch.t list;
+      p_postludes          : trailer list;
+      p_parameters         : Stretch.t list;
+      p_start_symbols      : Positions.t StringMap.t;
+      p_types              : (parameter * Stretch.ocamltype Positions.located) list;
+      p_tokens             : token_properties StringMap.t;
+      p_rules              : parameterized_rule StringMap.t;
+      p_on_error_reduce    : parameter list;
+    }
diff --git a/src/yacc-parser.mly b/src/yacc-parser.mly
index 8ed78f05fe13228737bfad09adc87cd6dcca480f..0a3105606fb6d06f28a65bcd74b67a69184fa6be 100644
--- a/src/yacc-parser.mly
+++ b/src/yacc-parser.mly
@@ -20,7 +20,7 @@ open Positions
 %token <Stretch.t Lazy.t> PERCENTPERCENT
 %token <Syntax.identifier option array -> Syntax.action> ACTION
 %start grammar
-%type <Syntax.grammar> grammar
+%type <Syntax.partial_grammar> grammar
 
 /* These declarations solve a shift-reduce conflict in favor of
    shifting: when the declaration of a non-terminal symbol begins with