Traditionally, errors in translation have been seen as primarily linguistic in nature. However, Mason (1987) helpfully distinguishes the following types:

• inversion of meaning;
• omission;
• addition;
• deviation;
• modification.

The seriousness of such errors should be measured in terms of the effect they have on the whole text:

• linguistic: does the error affect the main or secondary part of the sentence?
• semantic: does the error affect the main argument?
• pragmatic: does the error affect the intention of the message?