How to Add a Custom Word Dictionary for Domain-Specific Spelling

When you work with legal, medical, technical, or scientific documents in Word, the built-in dictionary often flags correct terms as misspelled. This happens because the standard dictionary does not include domain-specific vocabulary such as case names, drug names, or engineering jargon. Word lets you create custom dictionaries that store these specialized terms so they are no longer underlined in red. This article explains how to set up a custom dictionary, add words to it, and manage multiple dictionaries for different projects.

How Word Custom Dictionaries Work

Word uses a main dictionary for standard English spelling and one or more custom dictionaries for words you add. Each custom dictionary is a plain-text file with a .dic extension stored in the %AppData%\Microsoft\UProof folder. When you add a word via the right-click menu, Word adds it to the default custom dictionary named CUSTOM.DIC. You can create additional dictionaries for different domains, such as a legal dictionary and a medical dictionary, and switch between them depending on the document you are editing. This keeps your specialized terms organized and prevents one project’s jargon from cluttering another project’s word list.

Steps to Create a Custom Dictionary for Domain-Specific Spelling

1. Open the Custom Dictionaries dialog
   In Word, click File > Options > Proofing. Under the “When correcting spelling in Microsoft Office programs” section, click the Custom Dictionaries button.
2. Create a new dictionary
   In the Custom Dictionaries dialog, click New. Enter a name for your dictionary, for example “LegalTerms.dic” or “MedicalTerms.dic”. The dictionary is saved automatically to the UProof folder.
3. Set the new dictionary as the default
   Select the new dictionary in the list and click Change Default. This makes Word add all right-click additions to this dictionary instead of CUSTOM.DIC. If you prefer to keep CUSTOM.DIC as the default, skip this step.
4. Add words to the dictionary
   Select the dictionary and click Edit Word List. In the dialog, type each term in the “Word(s)” box and click Add. Repeat for every term you need. Click OK when finished.
5. Enable the dictionary for all documents
   Back in the Custom Dictionaries dialog, ensure the checkbox next to your dictionary is checked. Click OK to close all dialogs. Word now uses your custom dictionary during spell-check.

Adding Words On the Fly While Typing

You can add a word without opening the Options dialog. Right-click a word that is underlined with a red squiggle and select Add to Dictionary from the context menu. Word adds the word to the default custom dictionary. If you changed the default to your domain-specific dictionary, the word goes there. If you did not change the default, the word goes into CUSTOM.DIC. To move it later, use the Edit Word List feature to copy the word to the correct dictionary.

Managing Multiple Custom Dictionaries

If you work in multiple domains, you can keep separate dictionaries. For example, create one dictionary for legal terms and another for medical terms. Before starting a document, open the Custom Dictionaries dialog and uncheck the dictionaries you do not need. This prevents false positives where a medical term might be flagged as a misspelling in a legal document. You can also share a dictionary file with colleagues by copying the .dic file to their UProof folder and adding it through the Custom Dictionaries dialog.

Common Mistakes, Limitations, and Things to Avoid

Adding a word to the wrong dictionary

If you right-click and add a word without checking which dictionary is the default, the word may end up in CUSTOM.DIC instead of your domain-specific dictionary. Always verify the default dictionary in Custom Dictionaries before adding words on the fly.

Dictionary file not found when sharing

When you copy a .dic file to another computer, Word may not recognize it if the file is not in the correct folder. Place the .dic file in %AppData%\Microsoft\UProof and then add it via the Custom Dictionaries dialog. The dictionary must be added, not just placed in the folder.

Spell-check still flags words after adding them

If you add a word but the red squiggle remains, the word may already be in the document with a different case or formatting. Word dictionaries are case-insensitive, but a word with a trailing space or punctuation may not be recognized. Re-run the spelling checker by pressing F7 to clear the squiggles.

Accidentally deleting a dictionary

If you remove a dictionary from the Custom Dictionaries list, the .dic file is not deleted from the UProof folder. You can re-add it later by clicking Add and navigating to the file. To permanently delete a dictionary, close Word, delete the .dic file from the folder, and then remove it from the list in Word.

Custom Dictionary vs Exclude Dictionary

Item	Custom Dictionary	Exclude Dictionary
Purpose	Adds words so spell-check ignores them	Marks standard words as misspelled
File extension	.dic	.exc
Default location	%AppData%\Microsoft\UProof	%AppData%\Microsoft\UProof
How to create	File > Options > Proofing > Custom Dictionaries	Not available in the UI; create manually as a text file
Use case	Domain-specific jargon, proper names, acronyms	Common words you want to flag as errors (e.g., “color” vs “colour”)

Now you can create separate custom dictionaries for each domain you work in and switch between them as needed. Next time you start a document, open the Custom Dictionaries dialog and enable only the dictionary that matches the subject matter. For advanced control, use the Exclude Dictionary to flag words that the main dictionary accepts but your style guide rejects.