Update based on review

functions-and-operators/string-functions.md

@@ -1172,7 +1172,7 @@ Return a set of comma-separated strings that have the corresponding bit in bits
 
 ### [`MID()`](https://dev.mysql.com/doc/refman/8.0/en/string-functions.html#function_mid)
 
-The `MID(str, start, end)` function returns a substring starting from the specified `start` position and ends at the optinal `end` position.
+The `MID(str, pos, len)` function returns a substring starting from the specified `pos` position with the optinal `len` length.
 
 If any of the arguments are NULL the function returns NULL.