grandchild
grand‧child /ˈɡræntʃaɪld/
noun (plural grandchildren /-tʃɪldrən/) [countable]
the child of your son or daughter
grand‧child /ˈɡræntʃaɪld/
noun (plural grandchildren /-tʃɪldrən/) [countable]the child of your son or daughter