thirteenth UK /ˌθɜːˈtiːnθ/US /ˌθɝˈtiːnθ/noun 4adjective 1forms 1 noun4 •The person or thing in the thirteenth position. •The thirteenth day of a month. •One of thirteen equal parts of a whole. •The interval comprising an octave and a sixth. adjective1 •The ordinal form of the number thirteen. formsthirteenths
