A syntax error is an error in the syntax of a sequence of characters or tokens that is intended to be written in a particular programming language. It occurs when a programmer writes an incorrect line of code, such as missing punctuation or a misspelled name. Syntax errors are detected at compile-time for compiled languages. In interpreted languages, syntax errors are detected when the code is executed.

Some examples of syntax errors include missing or unmatched parentheses, inappropriate comma usage, and entering an invalid equation on a calculator. Type errors and undeclared variable errors are sometimes considered to be syntax errors when they are detected at compile-time.

It is important to recognize and understand common syntax errors to write efficient and confident code. Syntax errors can cause a program to not work, so it is crucial to correct them for the program to run correctly.