These functions, system variables, and keywords are obsolete because they are superseded by equivalent, usually better ones. We encourage you to use their replacements instead. Deprecated features are still available for use, but may be discontinued in future releases.
We originally defined many parameter qualifiers with multiple synonyms, thinking it would let you specify parameter lists more flexibly. On reflection, it makes more terms to recognize and remember, so we have chosen one preferred term and deprecate the others. See for details Function_Parameter_Qualifiers#Deprecated_Synonyms_for_Parameter_Qualifiers