A syntax error occurs when information is entered into a computer in an unrecognizable or improper format. If, for instance, an email address were to be typed with the word “dotcom” instead of “.com,” the message would be undeliverable because of a syntax error. Poorly or incorrectly formatted information might be entered by the programmer, a program user or even by the computer software itself. Computer programs can be viewed as forms of language, and as such, they have their own rules of grammar. When these grammar rules are violated, a syntax error occurs.

Syntax is a crucial element of clear communication in any language. For example, English has its own syntax, structure and grammar. Rules regarding spelling, sentence structure, word placement and punctuation help to convey ideas and make the intended meaning clear. Numbers also have their own rules and conventions that shape meaning as well, for instance making the price of $3.35 US Dollars distinct from the time 3:35 p.m. A syntax error would result from ignoring, forgetting or misusing these conventions.

The term "syntax error" is also frequently used to refer to semantic errors, where the information is in a recognizable but incorrect format. For instance, a familiar phrase such as “Who do you think you are anyway?” becomes much stranger when written as “Who do you think you are, anyway?” because of a simple semantic error involving a comma. There is nothing grammatically incorrect about the second format, but the intended meaning is unlikely to be understood.

People actually are quite good at working through syntax errors to find the intended message. For instance, text messaging is full of deliberate syntax errors and shortcuts to such a degree that it has evolved into its own dialect. Computers, on the other hand, lack human imagination and intuition and are simply unable to deduce intended meaning. A computer syntax error can cause a program to crash or freeze or might result in an error message. A syntax error sometimes can result in more subtle problems, causing a glitch or allowing a program to run with incorrect data.

Most common syntax and semantic errors stem from misspellings and incorrect punctuation. Programmers are responsible for catching syntax errors written into a computer program through testing, often with the help of debugging software to catch any logic problems. Many programs, despite being designed to interact with other software, can have trouble translating information from one format to another, which also can cause a syntax error.