Word has a built-in spell checker, thesaurus, dictionary and Office Assistant.
Normal.dot is the master template from which all Word documents are created. It is one of the most important files in Microsoft Word. It determines the margin defaults as well as the layout of the text and font defaults. Although normal.dot is already set with certain defaults, the user can change normal.dot to new defaults. This will change other documents that were created using the template and saved with the option to automatically update the formatting styles.
Like other Microsoft Office documents, Word files can include advanced macros and even embedded programs. The language was originally WordBasic, but changed to Visual Basic for Applications as of Word 97.
This extensive functionality can also be used to run and propagate viruses in documents. The tendency for people to exchange Word documents via email, USB key, and floppy makes this an especially attractive vector. A prominent example is the Melissa worm, but countless others have existed in the wild. Some anti-virus software can detect and clean common macro viruses, and firewalls may prevent worms from transmitting themselves to other systems.
These Macro viruses are the only known cross-platform threats between Windows and Macintosh computers and they were the only infection vectors to affect any Mac OS X system up until the advent of video codec trojans in 2007. Microsoft's released patches for Word X and Word 2004 effectively eliminated the Macro problem on the Mac by 2006.
Word's macro security setting, which regulates when macros may execute, can be adjusted by the user, but in the most recent versions of Word, is set to HIGH by default, generally reducing the risk from macro-based viruses, which have become uncommon.
As of Word 2007 for Windows (and Word 2004 for Macintosh), the program has been unable to handle ligatures defined in TrueType fonts: those ligature glyphs with Unicode codepoints may be inserted manually, but are not recognized by Word for what they are, breaking spellchecking, while custom ligatures present in the font are not accessible at all. Other layout deficiencies of Word include the inability to set crop marks or thin spaces. Various third-party workaround utilities have been developed. Similarly, combining diacritics are handled poorly: Word 2003 has "improved support", but many diacritics are still misplaced, even if a precomposed glyph is present in the font. Additionally, as of Word 2002, Word does automatic font substitution when it finds a character in a document that does not exist in the font specified. It is impossible to deactivate this, making it very difficult to spot when a glyph used is missing from the font in use.
Bullets and numbering
Users report that Word's bulleting and numbering system is highly problematic. Particularly troublesome is Word's system for restarting numbering. However, the Bullets and Numbering system has been significantly overhauled for Office 2007, which is intended to reduce the severity of these problems. For example, Office 2007 cannot align tabs for multi-leveled numbered lists, although this is a basic functionality in OpenOffice.org. Often, items in a list will be inexplicably separated from their list number by one to three tabs, rendering outlines unreadable. These problems cannot be resolved even by expert users. Even basic dragging and dropping words is usually impossible. Bullet and numbering problems in Word include: bullet characters are often changed and altered, indentation is changed within the same list, and bullet point or number sequence can belong to an entirely different nests within the same sequence.
Users can also create tables in MS Word. Depending on the version, Word can perform simple calculations. Formulae are supported as well.
AutoSummarize highlights passages or phrases that it considers valuable. The amount of text to be retained can be specified by the user as a percentage of the current amount of text.
According to Ron Fein of the Word 97 team, Auto Summarize cuts wordy copy to the bone by counting words and ranking sentences. First, AutoSummarize identifies the most common words in the document (barring "a" and "the" and the like) and assigns a "score" to each word--the more frequently a word is used, the higher the score. Then, it "averages" each sentence by adding the scores of its words and dividing the sum by the number of words in the sentence--the higher the average, the higher the rank of the sentence. "It's like the ratio of wheat to chaff," explains Fein. 
In Microsoft Office 2003, AutoCorrect items added by the user cease working when text from sources outside the document is pasted in.
Sub and superscript issues
In any of the Microsoft word package, it is impossible to display superscript exactly lying above subscript. It can only be done using equation editor.