The synthetic name of “Necessary Being in itself” is one of the most important names that Muslim philosophers, from Farabi to those of the present period, have used in their philosophical theology and, based on which, discussed the existence, attributes, and acts of God. In this paper, the writer has tried to analyze and explore the important points and ideas presented regarding this synthetic name through reviewing philosophical and kalami sources. The purpose here is twofold: to become familiar with some errors such as the “mixture of concept and referent” and the “mixture of the second philosophical intelligible with the first one”, which has occurred here, and to attain an accurate and defensible meaning of this name. In doing so, the writer initially demonstrates that two words of this synthetic name (being and necessary) are evident, polysemous, and secondary intelligibles and explains the importance of this point in the semantics of this name. Secondly, he analyzes and investigates the most important definitions provided for this name. From among the given six definitions, he criticizes the first and the fourth of them and pinpoints the sources of the errors committed in them. Later, while confirming the second, third, and fifth definitions, following Farabi, Ibn Sina, and Mulla Sadra, the writer chooses the definition of the Necessary Being in itself as a truth which is the same as existence as the best definition in a conceptual domain. Finally, he moves from the domain of “concept” to the domain of “existence” and provides an ontological interpretation of this name.