רָעָב ra`ab "famine. hunger". Understandably most used in books like Genesis (famine played an important role in the migrations of the Patriarchs), Ruth and Jeremiah (famine and seige tend to be associated).
In Amos only twice (both in one verse), in 8:11 where I have rendered it "hunger" because in English "hunger and thirst" form a pair, as רָעָב and צָמָא do in Hebrew. Though both the usage of the words in Hebrew and the cotext, where after mourning comes famine, suggests the stronger word captures the meaning better.