When will an Office application identify a word as misspelled that is not actually misspelled?

What will be an ideal response?

If a word is unrecognized by the application's dictionary, it is flagged as misspelled or grammatically incorrect. Misspellings are identified with a red wavy underline, grammatical problems are underlined in green, and word usage errors have a blue underline. If you right-click a word or phrase that is identified as a mistake, you will see a shortcut menu. If the application's dictionary has a suggestion as to the correct spelling, you can click to accept the suggestion and make the change. If a grammatical rule is violated, you will have an opportunity to select a correction. However, if the text is actually correct, you can click Ignore or Ignore All (to bypass all occurrences of the flagged error in the current document). Click Add to Dictionary if you want the word to be considered correct whenever it appears in all documents. Similar selections on a shortcut menu enable you to ignore grammatical mistakes if they are not errors.