What do we call the combination of symbols that forms a valid structure in programming languages?

The term that refers to the combination of symbols that forms a valid structure in programming languages is known as syntax. In programming, syntax is crucial because it defines the rules that govern how code is written. Each programming language has its own set of rules and conventions which dictate how statements and expressions should be structured. If the syntax is not followed, the code will result in errors and will not run as intended.

While the other terms mentioned relate to elements of programming, they do not specifically refer to the rules governing the valid combination of symbols. For instance, a code block is a section of code grouped together, often enclosed in braces or indentation, but it doesn’t encompass the rules of structure. An expression refers to a combination of variables, operators, and values that can be evaluated to produce a result, but it is only a part of what might be structured according to the rules of syntax. Lastly, structure is a more general term that can refer to various arrangements within programming but does not specifically denote the rules governing the assembly of code. Thus, syntax is the most precise term that captures the essence of the question.