diff --git a/inc/definition.h b/inc/definition.h
index c3c3621..eb79400 100644
--- a/inc/definition.h
+++ b/inc/definition.h
@@ -8,6 +8,28 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include <tokenizer.h>
+
+
+typedef enum
+{
+    CARROT_PATTERN_ELEMENT_VARIABLE_TERMINAL,
+    CARROT_PATTERN_ELEMENT_LITERAL_TERMINAL,
+    CARROT_PATTERN_ELEMENT_RULE
+} carrot_pattern_element_e;
+
+typedef enum
+{
+    CARROT_VARIABLE_TERMINAL_ALPHABETICAL_WORD,
+    CARROT_VARIABLE_TERMINAL_ALPHANUMERIC_WORD,         // 
+    CARROT_VARIABLE_TERMINAL_KEYWORD,                   // Subtype of CARROT_VARIABLE_TERMINAL_ALPHANUMERIC_WORD; from a list of user-specified keywords.
+    CARROT_VARIABLE_TERMINAL_OPERATOR,
+    CARROT_VARIABLE_TERMINAL_NUMBER,
+    CARROT_VARIABLE_TERMINAL_FLOAT,                     // Subtype of CARROT_VARIABLE_TERMINAL_NUMBER; all numbers, including those with digits after the number.
+    CARROT_VARIABLE_TERMINAL_INTEGER                    // Subtype of CARROT_VARIABLE_TERMINAL_NUMBER; only means full numbers without digits after the number.
+} carrot__variable_terminal_e;
+
+
 // carrot_definition_unit_s: A whole file (with possible included sub-files) of rules.
 //  A definition unit describes a single format or language.
 typedef struct      carrot_definition_unit              carrot_definition_unit_s;
@@ -37,26 +59,38 @@ typedef struct      carrot_pattern_element              carrot_pattern_element_s
 //  in exactly the way as it was stated in the definition.
 typedef struct      carrot_terminal                     carrot_terminal_s;
 
-struct carrot_definition {
+struct carrot_definition_unit
+{
+    uint32_t                                                    num_rules;
+    carrot_rule_definition_s                                   *rules;
 
+    carrot_token_stream_s                                      *token_stream;
 };
 
-struct carrot_rule_definition {
+struct carrot_rule_definition
+{
+    carrot_definition_unit_s                                   *syntax_definition;
 
+    uint32_t                                                    num_applying_patterns;
+    carrot_pattern_sequence_s                                  *applying_patterns;
 };
 
-struct carrot_pattern {
+struct carrot_pattern_sequence
+{
+    // rule: The rule that this pattern sequence belongs to.
+    carrot_rule_definition_s                                   *rule;
 
+    uint32_t                                                    num_items;
+    carrot_pattern_element_s                                   *items;
 };
 
-struct carrot_pattern_element {
+struct carrot_pattern_element
+{
+    carrot_pattern_element_e                                    type;
+    carrot__variable_terminal_e                                 variable_terminal;
+    char                                                       *referenced_rule_name;
+    char                                                       *literal_terminal;
 
 };
 
-struct carrot_terminal {
-
-};
-
-
-
 #endif