What common error occurs when a letter or word is not typed at all?

The term "omitted" accurately describes the situation where a letter or word is not typed at all. This type of error indicates that something was intended to be included in the text but was left out entirely, resulting in incomplete communication. Recognizing an omitted letter or word is crucial because it can change the meaning of the sentence and may lead to confusion for the reader.

Other choices might imply a similar situation, but they don't capture the specific nature of the error as well as "omitted." For instance, "missed" and "skipped" could imply that something was overlooked in the process, but do not specifically denote absence in typing. "Ignored" suggests a deliberate choice to not include something, which does not accurately reflect the accidental nature of a typing error. Therefore, "omitted" is the correct term that conveys that a letter or word was not typed intentionally or unintentionally, resulting in a gap in the text.