SV, or System Verilog, is a high-level hardware design language used for verifying hardware designs and conducting system-level testing. Synonyms that can be used in place of SV include HDVL (Hardware Design and Verification Language), Verilog, VHDL (VHSIC Hardware Description Language), and RTL (Register Transfer Level). Verilog and VHDL are both hardware description languages that can be used to describe circuits and systems. HDVL is a generic term that encompasses both Verilog and VHDL. RTL is a level of abstraction used to describe the behavior of digital circuits. Each of these synonyms has its own unique features and advantages, making them useful in different scenarios.