diff --git a/expr_grammar b/expr_grammar
new file mode 100644
index 0000000..49b14a1
--- /dev/null
+++ b/expr_grammar
@@ -0,0 +1,10 @@
+expression -> equality ;
+equality   -> comparison ( ( "!=" | "==" ) comparison )* ;
+comparison -> term ( ( ">" | ">=" | "<" | "<=" ) term )* ;
+term       -> factor ( ( "-" | "+" ) factor )* ;
+factor     -> exponent ( ( "/" | "*" | "/." | "/_" | "%" | "/%" ) exponent )* ;
+exponent   -> unary ( ( "**" ) unary )* ;
+unary      -> ( "!" | "-" ) unary
+           | primary ;
+primary    -> NUMBER | STRING | "true" | "false" | "nil"
+           | "(" expression ")" ;