Aluf (אלוף) is the term used for General and Admiral in the Israel Defense Forces. In addition to the Aluf rank itself, there are four other ranks which are derivatives of the word. Together, they constitute the five highest ranks in the IDF.
Rav Aluf is usually translated as "Lieutenant General," but is often considered to equate to a full General, since it is the most senior rank. The rank is given only to the Ramatkal (Chief of the General Staff), so there can only be one active Rav Aluf under regular circumstances. However this could change in a time of war. During the Yom Kippur War in 1973, retired rav aluf Haim Bar-Lev was called back into service, replacing Shmuel Gonen as the commander of the southern front. Thus, along with chief of the general staff David Elazar (who succeed Bar-Lev in that position the previous year), there were two people in active service holding the rank of rav aluf simultaneously.
Israel is essentially a land power and air power, with the navy being apportioned less than five percent of the military budget. Consequently, there are no separate naval ranks, and "Aluf" can be an Admiral as well as a General.
The term "Aluf" is taken from the Bible, where it was a rank of nobility among the Edomites, ancient Judea's neighbors (and often, enemies) to the south. It comes from an archaic root meaning "to be attached to". The term is used in at the conclusion of the lengthy genealogy of Esau found in to refer to the Edomite chieftains who were his descendants. In modern Hebrew as spoken in contemporary Israel it can mean "champion" as well as being a military rank.
The non-Hebrew word "general" was also taken into Hebrew (גנרל), and is used to refer to the generals of foreign armies. It can also be used colloquially in reference to a senior Israeli officer, in a derogatory sense - implying that the officer concerned is over-officious, incompetent, and/or involved in internecine power struggles with other officers, to the neglect of proper military duties.