Instead of starting with a built-in dictionary, Word 2013 links you to the Office Store so you can pick a free dictionary or buy one from a collection, including dictionaries in many languages.
To choose and install the dictionary you want, right-click any word and click Define.
Or click Review > Define.
Sign in if you’re prompted to, and look over the choices in the Dictionaries list, and then click Download to install the dictionary you want.
After it downloads, the dictionary will open automatically in Word. From then on it will open whenever you click Define.
Once you’ve downloaded one dictionary, go to the Office Store if you want more.
To start using a new app, such as a dictionary, find and double-click it in the apps list.