I previously posted how to add a medical dictionary to Word 2010. It’s a simple matter of copying a file and adding it to Word. Although the concept is the same with Word 2011 on a Mac operating system, implementation on a Mac requires some additional effort. For those of you who aren’t Mac power users, I’ve provided screen captures detailing the tricks you must know to achieve success.
The file you need is downloaded from here where where I posted how to add a custom dictionary to Word 2010 on Windows 7. Scroll almost to the bottom of the post and right-click the OpenMedSpel100.zip link to open the download menu. Select the Download Linked File As option.

Figure 1. Right-click the link and select Download Linked File As.
Next, you must specify a file name and location for the dictionary file. You can use any file name and location. I chose en_US_OpenMedSpel100 for the file name and the Microsoft Office 2011 folder for the location.

Figure 2. Under Favorites, select Applications, then select Microsoft Office 2011. Provide a meaningful name for the file (I used en_US_OpenMedSpell100) and click Save.
You will need to navigate to your Microsoft Office 2011 folder and open the downloaded zip file to extract the dictionary file. You can do this by opening your Documents folder, then selecting Applications, and finally selecting Microsoft Office 2011. You can delete your zip file after extracting its contents if you want to keep your folders neat and clean.

Figure 3. Navigate to the Microsoft Office 2011 folder and open the zip file.
Go to Word’s menu and select Preferences as shown.

Figure 4. Select and open Word’s Preferences menu.

Figure 5. Select Spelling and Grammar on the Preferences dialog box.

Figure 6. Click the Dictionaries button on the Spelling and Grammar dialog box.

Figure 7. Click the Add button to add the custom dictionary.

Figure 8. The dictionary file appears but is not selectable. Select All Files to make it selectable.

Figure 9. Select your custom dictionary file and click the Open button.

Figure 10. Click OK to finish adding the custom dictionary file.