SetAttributes

SetAttributes[symbol,attr] adds attr to the list of attributes of the symbol symbol. 

SetAttributes["symbol",attr] adds attr to the attributes of the symbol named "symbol" if it exists.

SetAttributes[s,{attr1,attr2,…}] sets several attributes at a time.

SetAttributes[{s1,s2,…},attrs] sets attributes of several symbols at a time.

Please visit the official Wolfram Language Reference for more details and examples on core symbols.