mandarin: shrub or small tree having flattened globose fruit with very sweet aromatic pulp and thin yellow-orange to flame-orange rind that is loose and easily removed; native to southeastern Asia
citrus: any of numerous tropical usually thorny evergreen trees of the genus Citrus having leathery evergreen leaves and widely cultivated for their juicy edible fruits having leathery aromatic rinds
old man: a man who is very old