If you use Microsoft Word, then you should know that apart from checking text for spelling mistakes it will also check for our grammar. To have your grammar checked, either press F7 or go to Tools and then Spelling and Grammar. You will see a dialog window and at the bottom left part of it check grammar options. If you want MS Word to check your grammar, check this box. If not, then leave it unchecked. Although grammar checking option in Word helped me a few times, I do not always follow its suggestions as very often they seem rather awkward and inaccurate. I guess it is still not so easy for a grammar checking program to to fully understand the English language. Try to experiment a little and click on Options button located at the bottom of the window. You will see that you are given a choice which writing style your grammar should be check according to. These options include: Formal, Casual, Standard, Technical and Custom.
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