What is the correct syntax for defining a variable in JavaScript?

The correct syntax for defining a variable in JavaScript can be achieved using several keywords, including 'var' and 'let'.

Using 'var' is a traditional way of declaring a variable. When you use var myVariable;, it creates a variable named myVariable that can be assigned a value later. This syntax is straightforward and has been part of JavaScript since its inception.

Additionally, using let myVariable; is also valid and represents a more modern approach to variable declaration. 'let' allows for block-scoped variables, giving developers flexibility with variable scope. While both 'var' and 'let' are correct for variable declaration in their respective contexts, the more traditional syntax highlighted in the question reflects the foundational way of defining variables in JavaScript.

The other options do not conform to JavaScript syntax for variable declaration. 'define myVariable;' and 'set myVariable;' are not recognized keywords in JavaScript, making them invalid. Hence, the choice that communicates the correct syntax must align with established JavaScript language rules.