Language simplicity allows programs to be expressed concisely. Language simplicity supports programming that is easy to write, read and understand. Orthogonal language allows all possible combinations of the language's features with every combination being meaningful. The semantics of the original constructs in the language remain unchanged by the addition of the new construction. Correctness and standards Rigorous definition of the meaning of each language construct.
Syntax is easy to define.
Semantics may be difficult to document especially in a highly orthogonal language where a construct can be used many different ways. Syntax Writability - how easy is it to undestand the commands and write programs that do what you want them to do. How well does the language perform to its specifications under all conditions. Readability and writability - programs that are easy to understand will naturally be more reliable. Cost - factors into the overal cost of a project.