bit-select

A bit-select is a variable, constant, or constant expression that addresses a particular bit of a vector net or register. The variable, constant, or constant expression is enclosed in brackets. A bit-select is sometimes called an "index."

See "Section 4.2.1: Bit-Select and Part-Select" in the IEEE Std 1364-1995 IEEE Standard Hardware Description Language Based on the Verilog Hardware Description Language manual for more information.