creation of function

I cannot create any function / procedure on MariaDB version 10.5.8.

I tried to use the function creation demo on the site:

CREATE FUNCTION hello (s CHAR(20))

RETURNS CHAR(50) DETERMINISTIC

RETURN CONCAT('Hello, ',s,'!');

It return me this error:

/* SQL Error (1064): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'RETURNS CHAR(50) DETERMINISTIC

RETURN CONCAT('Hello, ',s,'!')' at line 2 */

/* Affected rows: 0 Found rows: 0 Warnings: 0 Duration for 0 of 1 query: 0.000 sec. */

I tried looking for solution online, but to no avail, nothing help.

Please help! Thanks