Sample space is referred as the set of all possible outcomes of a random experiment.And is denoted by the symbol 'S'

$\therefore$ A coin is tossed three times,the possible outcomes are :

{HHH,HHT,HTT,THH,HTH,THT,TTH,TTT}

Where H represents Head,T represents Tail

$\therefore$ The sample space S={HHH,HHT,HTT,THH,HTH,THT,TTH,TTT}