Update grammar

grammar

@@ -39,7 +39,11 @@ Mixture ::=
 
 /* Preposition: */
 /* Used to link nouns, pronouns, or phrases to other words within a sentence */
-Preposition ::= ("with" | "to" | "in" | "of" | "at" | "for" | "off" | "on" | "over" | "under")? ( "a" | "the")?
+Preposition ::= ("with" | "to" | "in" | "of" | "at" | "for" | "off" | "on" | "over" | "under")?
+
+/* Preposition: */
+
+Article ::= ( "a" | "an" | "the")?
 
 at, for, in, off, on, over, and under
 /* Conjunction */