What constitutes a syntax error?

A syntax error occurs when the code is improperly structured, meaning it does not conform to the rules of the programming language being used. This type of error is caught by the compiler or interpreter before the code is run. For example, if a programmer forgets to close a parenthesis, or uses incorrect punctuation, the language's syntax rules are violated, and this will stop the program from compiling or executing.

The other options refer to different aspects of programming errors. For instance, when code runs but yields incorrect results, it is known as a logical or runtime error, not a syntax error. A lack of variable declarations can lead to issues during execution but does not fall under the category of syntax errors; it may result in a different type of error altogether, depending on the language's rules about variable scope and declaration. Regarding arguments provided to functions, if they are incorrect in terms of type or number, it could lead to runtime errors rather than syntax errors. Thus, the core of what defines a syntax error is the improper structuring of code, as it directly relates to how the code is compiled or interpreted.