diff --git a/docs/en/sql-reference/functions/string-functions.md b/docs/en/sql-reference/functions/string-functions.md
index 6b95796db03..bd24d2307dc 100644
--- a/docs/en/sql-reference/functions/string-functions.md
+++ b/docs/en/sql-reference/functions/string-functions.md
@@ -571,6 +571,7 @@ SELECT upper('clickhouse');
 
 Converts a string to lowercase, assuming that the string contains valid UTF-8 encoded text. If this assumption is violated, no exception is thrown and the result is undefined.
 
+Does not detect the language, e.g. for Turkish the result might not be exactly correct (i/İ vs. i/I).
 
 If the length of the UTF-8 byte sequence is different for upper and lower case of a code point, the result may be incorrect for this code point.
 
@@ -734,13 +735,13 @@ concat(s1, s2, ...)
 
 **Arguments**
 
-Values of arbitrary type. Empty argument is also allowed.
+Values of arbitrary type.
 
 Arguments which are not of types [String](../data-types/string.md) or [FixedString](../data-types/fixedstring.md) are converted to strings using their default serialization. As this decreases performance, it is not recommended to use non-String/FixedString arguments.
 
 **Returned values**
 
-The String created by concatenating the arguments. If there are no arguments, the function returns empty string.
+The String created by concatenating the arguments.
 
 If any of arguments is `NULL`, the function returns `NULL`.