What defines the rules for combining elements of a programming language to form legal statements?

The aspect that defines the rules for combining elements of a programming language to form legal statements is syntax. Syntax encompasses the set of rules and guidelines that dictate how symbols, keywords, and statements must be arranged in code to be valid and correctly understandable by a compiler or interpreter. Essentially, it refers to the structure of the code itself, ensuring that programmers write code in a way that the programming language can interpret.

In contrast, semantics relates to the meaning of those statements; it addresses what the statements do when executed. Structure might refer more broadly to the organization of code within a program, such as how functions and classes are constructed, rather than to the rules governing individual statements. Logic pertains to the reasoning and flow of operations within the program, rather than to the formal arrangement of language elements. Thus, syntax is the cornerstone that allows programmers to create coherent and functioning code within a programming language.