Your Mac has a powerful built-in Dictionary app that integrates directly with macOS. It allows you to look up definitions by force-touching a word, using Spotlight search, or right-clicking text in Safari. While the default dictionaries provided by Apple (such as the New Oxford American Dictionary) are excellent, you can add custom dictionaries to macOS to look up highly specific medical terminology, legal jargon, or foreign language definitions.
How to Download and Add a Custom Dictionary
Apple supports the .dictionary file format. You can download custom, open-source dictionary files from various developer communities online, such as GitHub. Once you have downloaded a .dictionary folder, follow these steps to install it on your Mac.
- Open the Dictionary app on your Mac (you can find it in your Applications folder or by searching via Spotlight).
- In the top menu bar, click on File, then select Open Dictionaries Folder.
- A Finder window will open, displaying a hidden
Dictionariesfolder located inside your Mac’s Library. - Drag and drop the custom
.dictionaryfolder that you downloaded into this window. - Close the Finder window and completely quit the Dictionary app (Cmd + Q).
How to Enable the New Dictionary
Just because the dictionary file is installed does not mean your Mac is using it yet. You must manually activate it in the app’s preferences.
- Re-open the Dictionary app.
- In the top menu bar, click on Dictionary, then select Settings (or Preferences on older versions of macOS).
- Scroll through the list of available reference sources. Your newly installed custom dictionary will appear at the bottom of the list.
- Check the box next to your custom dictionary to enable it.
You can also click and drag the dictionaries in this list to rearrange their priority. If you place your custom dictionary at the top of the list, your Mac will prioritize its definitions over the default Oxford Dictionary when you use the force-touch lookup gesture or Spotlight search.