The red line indicates a misspelled word.
The blue line indicates a grammatical error, including misused words.
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A misused word—also known as a contextual spelling error—occurs when a word is spelled correctly but used incorrectly. For example, if you used the phrase Deer Mr. Theodore at the beginning of a letter, deer would be a contextual spelling error. Deer is spelled correctly, but it is used incorrectly in the letter. The correct word is Dear.
To correct spelling errors:
Right-click the underlined word, then select the correct spelling from the list of suggestions.
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The corrected word will appear in the document.
You can also choose to Ignore All instances of an underlined word or add it to the dictionary.
To correct grammar errors:
Right-click the underlined word or phrase, then select the correct spelling or phrase from the list of suggestions.
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The corrected phrase will appear in the document..