Wikipedia is the only dictionary source after upgrading to macOS Catalina.

I had this problem but solved it using a Time Machine backup from before I updated. I had updated to Catalina (10.15.4) from Sierra when the problem arose.

1. Open Dictionary app. Go to File> Open Dictionaries Folder. Leave this open.
2. Go to Volumes/"Your Backup Drive"/Backups.backupdb/"Your Computer"/"Date of Backup" *this backup should be before you updated to Catalina*/Macintosh HD/System/Library/Assets/com_apple_MobileAsset_DictionaryServices_dictionaryOSX
3. Open the folders in there you will find folders named "Asset Data". Your dictionary files should be there.
4. Copy dictionary files to the "Dictionaries" folder from step one.
5. They should now appear in the Dictionaries app for use.

I have attached a photo of the file path for ease.

First boot into Safe Mode (How to use safe mode on your Mac - Apple Support) by booting with the Shift key held down and check there to see if the problem persists.  Reboot normally and test again.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing some system cache cleaning, volume verifying and directory repairing. 

Next, try the following: download and apply the macOS Catalina 10.15.4 Combo Update and check to see if you get the full compliment of dictionaries.

Not sure why no one did this yet, but I have uploaded the files for everyone to download (after getting them from a friends Mac).

Heres the link: https://easyupload.io/tr7mn5

Place them here: /Users/your-name/Library/Dictionaries

Vote as "Helpful" ⬇︎ if I solved your problem!

d-gon wrote:

I used to be able to right-click a word and select Look Up to get definitions in previous OS. After upgrading to Catalina I now have Wikipedia as the only source in the Dictionary App and don't see an option to add other dictionaries.

Thanks in advance for your input.

You can manually add more dictionary sets to the Dictionary app.

Dictionary.app>Preferences> add dictionaries

Look up words on Mac - Apple Support

https://support.apple.com/guide/dictionary/welcome/mac

If you followed the steps I outlined above and you really only have Wikipedia and the Oxford Dictionaries aren't hiding on your drive, ANd you haven't done a clean install of Catalina, then all I can recommend trying is to install the original OS that came with your computer, back up the dictionary files to a thumb drive, and then update to Catalina. Yes, this will take a long time, and may not even solve the problem, but it is worth a try. I say "update to Catalina" since this will maintain the files from the earlier OS that do not need updating and will just install the newest ones, so the Oxford dictionaries should remain during the upgrade. If they don't you have them on a thumb drive and can install them manually.

To reinstall: https://support.apple.com/guide/mac-help/reinstall-macos-mchlp1599/mac

If the version of MacOs that came with your Mac is not available, choose Mojave or High Sierra from the drop-down list.

Note that the dictionaries are 6-7 folder layers down, so be sure to write down their locations so you can put them in the correct folder. Use Spotlight to search for "Oxford" and you should see something like "file://System/Library/Assets2/..." (and more) next to the search term at the top of the window. Write all that down, that is where the dictionary goes.

Good luck!

I had this exact same issue when I upgraded to the latest Catalina (10.15.5) a couple of hours ago. I contacted Apple Support, and the issue got fixed as easily as just following three steps:

1. Reboot the Mac into safe mode: hold the shift key continuously as soon as the Mac starts up until there is the "safe mode" appearing on the top right corner.
2. Open Dictionary, and if this method works, your previous dictionaries should all be there.
3. Restart again and you'll see them in the regular mode.

Just an option for those who do not have backup disk available. Hope this works for everyone!

Hi Muvinco,

I tried your suggestion using a backup from before I installed Catalina. I followed the correct file path, but unfortunately I could find an Assets folder, even after showing hidden files. Are you able to provide an explanation for why my Assets folder is not showing or missing? Thank you.

I've been facing the same problem ever since I upgraded to Catalina a few days ago. After reading millions of responses on how to fix it, and just when I was on the brink of giving up, I finally managed to solve the problem and restore my dictionary resources! I was actually inspired by Muvinco's reply to this thread, but I had to add a few minor tweaks to his steps for the solution to work for me. So a big thank you to Muvinco!

The problem I faced when applying Muvinco's suggestion was that when I opened my Time Machine, I was only able to access backup dates from AFTER my upgrade. But what I needed was to restore the Dictionary I had BEFORE the upgrade. So, and since I usually back up all my files to an external hard drive, I had to connect my hard drive to my mac for Muvinco's solution to work.

In brief, what we'll need for this solution is to go back to a back-up from Time Machine that predates the date of our upgrade, and restore the folder to our Desktop or Library. It's very simple, I'm no tech expert at all, but this is actually very easy to follow. So don't give up just yet guys, you've got this!

Important: My external hard drive was my entry point to the solution, so if you guys have your files backed up on an external hard drive, you should be able to have your dictionary resources back by following the steps below:

1- Connect your external hard drive to your MacBook (on the importance of this step: the external hard drive allows you to access files and applications on Time Machine that you had on your MacBook from before the date of your upgrade, and that's exactly what you'll need).

2- Open the Time Machine app from your Applications Folder, or by typing Time Machine in your Spotlight Search as shown in the picture below

3- After you open the Time Machine app, wait a bit for your earlier backup dates to show up. Once shown, choose any backup you've done before your upgrade. For example in my case, I upgraded to Catalina in April 2020, so I chose a backup I did on January 12, 2020, as shown below:

4- On your Time Machine, go to your Macintosh HD --> Library --> Dictionaries, and restore the entire Dictionaries Folder by simply clicking on "Dictionaries", then "Restore".

5- Now this will restore your old Dictionaries folder to your current MacOs. If prompted to choose a location for your restored folder, just choose Library in your Macintosh HD (or Desktop and then move to Library); if not, it will automatically be restored into Library anyway.

6- Open your Dictionary application (the one broken with only Wikipedia as a resource) from your MacBook, go to File --> Open Dictionaries Folder and leave this folder open.

7- Now go back to your Macintosh HD --> Library --> Dictionaries (this should be the folder you just restored from your Time Machine/hard drive -- shown in the picture below), and move all the resources you have on it to the Dictionaries Folder you opened in step 6.

8- Finally, relaunch your Dictionary app, go to Preferences, and you should now be able to see all the resources you moved from Step 7, as shown below. Et voilà :) Problem should be solved!

I hope I didn't miss any step, and hope this helps you guys!!

Cheers,

Rana

Thanks. My dictionary only had Wikipedia and now it's fixed.

I had another work around since I upgraded from Yosemite to Catalina. I hope this would help others as well.

In my Time Machine backup from Yosemite, I didn't have the same folder structure where the the Dictionaries are stored.

Instead they were in MacintoshHD/Library/Dictionaries/

I copied all those .dictionary Files into the Dictionary Folder of the Dictionary App

You can access that by Opening the Dictionary App and Go to File > Open Dictionaries Folder

Then simply copy all the .dictionary files in there.

Quit Dictionary App and Open it again then go to Preferences or CMD + , (shortcut). There you can check all the Dictionaries you want to use.

Thanks so much guys! I had to go through different support threads but you all helped.

Hey Cas606,

I am not sure why your Assets folder is not showing up, sorry. My only suggestion would be to spotlight files with ".dictionary" extension in your system and see if you find the files that way.

Hope this helps.

Hi Muvinco,

Thanks, this worked! When I searched .dict files in a backup I found them in a Dictionaries folder stored in Library (but a different Library folder to the folder in System). Hope that makes sense! Anyway, I copied the dictionaries from the backup into the application Dictionaries folder and they are now all there. Thanks again, very helpful :)

A slightly different version of this worked for me. I was confused for a while, but this is what I did:

I left the "Dictionaries" folder open on my computer as suggested by muvinco

(I opened the Dictionary app and then clicking File > Open Dictionaries Folder)

Then found the dictionary packages in my Time Machine backup:

Macintosh HD > System > AssetsV2 > com_apple_MobileAsset_DictionaryServices_dictionaryOSX > [folderwithlongname.asset] > AssetData

(I did have an Assets folder, but it didn't contain a com_apple_MobileAsset_DictionaryServices_dictionaryOSX folder.)

There were three folders with the long name (eg something like 8f75a23jkhjkhkjhjhkhkh.asset). Each of these long folders had a different AssetData folder - one for each of the dictionaries I had installed previously.

I copied just the packages (eg "Apple Dictionary.dictionary") and pasted them into the dictionaries folder I'd left open from the Dictionary app. I was then able to tick the boxes to add these in the preferences window.

Dictionary is now working properly. Hope this is useful to someone!

Then I suggest you contact Apple Support. The chat option worked pretty effectively for me. They responded quickly. Tell them the context of your issue (no backup disk and safe mode reboot didn't work....etc.) so that they can rule out possible causes and stuff. Good luck!

I have Mac OS Catalina 10.15.5 and my Dictionary app shows New Oxford American dictionary, Oxford American Writer's Thesaurus, Apple Dictionary, and Wikipedia. Open the Dictionary app and look at its Preferences. They may be there, unchecked.