The chapter discusses the nomenclature of voltage-gated sodium channels, which are crucial for initiating and propagating action potentials in excitable cells. These channels consist of an α subunit (~260 kDa) and β subunits, with the α subunit being essential for functional expression and the β subunits modifying channel kinetics and voltage dependence. Various sodium channels have been identified through electrophysiological recording, biochemical purification, and molecular cloning. Despite their similar functional properties, sodium channels lack a consistent nomenclature, leading to multiple synonyms and numerical names. To address this issue, a standardized nomenclature is proposed, based on the system used for voltage-gated potassium channels. This new nomenclature uses a numerical system to define subfamilies and subtypes, with the chemical symbol "Na" followed by the physiological regulator "voltage" as a subscript. The number after the subscript indicates the gene subfamily, and the number after the decimal point identifies the specific isoform. The nine mammalian sodium channel isoforms are highly similar in amino acid sequence, suggesting they may be part of a single family. Phylogenetic analysis supports this hypothesis, with all nine isoforms being more closely related to each other than to other families. However, some isoforms, such as Na,1.4 and Na,1.6, have a more distant evolutionary relationship and are located on different chromosomes. Additionally, closely related sodium channel-like proteins have been identified but have not yet been functionally expressed. These proteins show significant differences in critical regions but are still highly similar to other sodium channels. The chapter also discusses the potential for additional auxiliary subunits and proposes a naming system for these subunits. The authors hope that this standardized nomenclature will facilitate communication and comparison of research on sodium channels. The nomenclature has been reviewed and accepted by the Nomenclature Committee of the International Union of Pharmacology.The chapter discusses the nomenclature of voltage-gated sodium channels, which are crucial for initiating and propagating action potentials in excitable cells. These channels consist of an α subunit (~260 kDa) and β subunits, with the α subunit being essential for functional expression and the β subunits modifying channel kinetics and voltage dependence. Various sodium channels have been identified through electrophysiological recording, biochemical purification, and molecular cloning. Despite their similar functional properties, sodium channels lack a consistent nomenclature, leading to multiple synonyms and numerical names. To address this issue, a standardized nomenclature is proposed, based on the system used for voltage-gated potassium channels. This new nomenclature uses a numerical system to define subfamilies and subtypes, with the chemical symbol "Na" followed by the physiological regulator "voltage" as a subscript. The number after the subscript indicates the gene subfamily, and the number after the decimal point identifies the specific isoform. The nine mammalian sodium channel isoforms are highly similar in amino acid sequence, suggesting they may be part of a single family. Phylogenetic analysis supports this hypothesis, with all nine isoforms being more closely related to each other than to other families. However, some isoforms, such as Na,1.4 and Na,1.6, have a more distant evolutionary relationship and are located on different chromosomes. Additionally, closely related sodium channel-like proteins have been identified but have not yet been functionally expressed. These proteins show significant differences in critical regions but are still highly similar to other sodium channels. The chapter also discusses the potential for additional auxiliary subunits and proposes a naming system for these subunits. The authors hope that this standardized nomenclature will facilitate communication and comparison of research on sodium channels. The nomenclature has been reviewed and accepted by the Nomenclature Committee of the International Union of Pharmacology.