extract function is used to extract year, month, or date from a date or timezone hour or timezone minute from an interval. Examples:

extract(DAY FROM DATE '2011-01-02') 	-- 02
extract(MONTH FROM DATE '2011-01-02') 	-- 01
extract(YEAR FROM DATE '2011-11-11') 	-- 2003

extract function was introduced in Oracle 9i and it is supported in Oracle 10g and 11g.