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Microsoft Word 365 marks unfamiliar names, technical terms, brand names, abbreviations, and industry-specific language as spelling errors when they are not in its dictionary. Adding those words to a custom dictionary tells Word to accept them in future documents, so the red underline no longer appears.
You can add words directly from the right-click spelling menu, through Word’s proofing settings, or by editing a custom dictionary file. These options are useful whether you need to save one word quickly, manage several specialized terms, or keep a consistent vocabulary across your documents.
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If Word keeps flagging a word after you add it, the issue is often related to language settings, disabled custom dictionaries, file permissions, or the wrong dictionary being selected. The steps below cover both the main ways to add words and the common fixes when the dictionary does not behave as expected.
Add a Word to the Dictionary from the Right-Click Menu
The quickest way to add a custom word in Word 365 is from the spelling menu that appears when Word marks a word with a red wavy underline. This is best for names, product terms, acronyms, technical vocabulary, and other correct words that Word does not recognize. Once added, the word should stop being flagged in current and future documents that use the same proofing language and custom dictionary.
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- Open your document in Word 365.
- Find the word with the red wavy underline.
- Right-click the underlined word.
- Select Add to Dictionary from the menu.
After you choose Add to Dictionary, Word adds that exact spelling to the active custom dictionary. For example, if your company name is ContosoX, adding ContosoX will not automatically add contosox, CONTOSOX, or plural forms unless Word treats them as acceptable based on its proofing rules. Add the form you actually use in your documents.
If you do not see Add to Dictionary, check the menu carefully. In some versions of Word 365, the spelling menu may show suggested corrections first, along with options such as Ignore All. Ignore All only hides the spelling warning in the current document session or document context; it does not permanently add the word to your dictionary. Use Add to Dictionary when you want Word to remember the word beyond the current file.
When this method works best
- Single custom terms: Add one name, brand, acronym, or specialized term as you encounter it.
- Fast cleanup: Remove repeated red underlines while editing a document.
- Personal vocabulary: Save words that are correct for your work but uncommon in the standard Word dictionary.
Be careful not to add misspelled words by accident. If you right-click a typo and add it to the dictionary, Word may stop warning you about that incorrect spelling later. If you are unsure, choose one of Word’s suggested corrections instead, or verify the spelling before adding it. You can remove mistaken entries later through the custom dictionary settings, but it is faster to add only confirmed words from the start.
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If you do not want to wait until Word underlines a term in your document, you can add it through the Word 365 proofing options. This method is useful for names, product terms, industry vocabulary, acronyms, and branded spellings that you use often. It also gives you more control because you can choose which custom dictionary receives the new word.
To add a word through the settings in Word 365 for Windows, open Word and select File in the upper-left corner. Choose Options, then select Proofing from the left menu. In the section labeled When correcting spelling in Microsoft Office programs, click Custom Dictionaries. Select the dictionary you want to use, such as CUSTOM.DIC, then choose Edit Word List. Type the word exactly as you want Word to recognize it, click Add, then click OK to close each window.
- Go to File > Options.
- Select Proofing.
- Click Custom Dictionaries.
- Choose the active dictionary, usually CUSTOM.DIC.
- Click Edit Word List.
- Enter the custom word and select Add.
- Click OK to save the change.
When you type the word into the list, match the spelling and capitalization you want Word to accept. For example, adding ContosoX may not always treat contosox or CONTOSOX the same way in every proofing context. If your organization uses a stylized name, such as eDiscovery or PowerApps, enter the preferred form. You can add alternate versions separately if people commonly use more than one capitalization style.
On Word for Mac, the path is slightly different. Open Word, choose Word from the menu bar, then select Preferences. Under Authoring and Proofing Tools, choose Spelling & Grammar, then open the dictionaries or custom dictionary options available in your version. From there, you can edit the word list and add the term. Microsoft occasionally changes labels in Word 365 updates, so look for wording such as Custom Dictionaries, Dictionaries, or Edit if the exact button name differs.
This settings-based method is also helpful when the right-click Add to Dictionary option is unavailable or grayed out. That can happen when Word is checking text in a different language, when the document is protected, or when the active dictionary is not set up correctly. Adding the term directly through Proofing confirms that Word has a writable custom dictionary selected and that the word is being stored in the place Word uses for spelling checks.
Manage Custom Dictionaries in Word 365
Word 365 stores added spellings in one or more custom dictionaries. Managing these dictionaries is useful when you want to choose where new words are saved, create a separate dictionary for a project, enable a shared company word list, or stop Word from using an old dictionary. You can access these controls from Word’s proofing options.
- Open Word 365.
- Select File > Options.
- In the Word Options window, choose Proofing.
- Select Custom Dictionaries.
The Custom Dictionaries window shows the dictionaries Word can use for spell checking. A checked dictionary is active. The dictionary marked as the default is where Word saves new words when you use Add to Dictionary. If a dictionary is listed but not checked, Word will not use its contents during spell checking.
Choose the default dictionary
If Word is saving new words to the wrong place, select the dictionary you want to use, then choose Change Default. For most users, the default file is named CUSTOM.DIC. If you work with different types of documents, you can create separate dictionaries, such as one for client names, one for medical terms, or one for product names.
- New: Creates a new custom dictionary file.
- Add: Connects an existing dictionary file to Word.
- Remove: Removes the selected dictionary from Word’s list without necessarily deleting the file from your computer.
- Edit Word List: Opens the selected dictionary so you can add, delete, or review entries.
Set the dictionary language
Each custom dictionary can be linked to a specific language. In the Custom Dictionaries window, select a dictionary and check the Dictionary language setting. If it is set to All Languages, Word can use it across documents in different proofing languages. If it is set to a specific language, such as English (United States), Word uses it only when the text is marked with that language.
This matters when a word you added still appears with a red underline. For example, if your document text is set to English (United Kingdom) but the custom dictionary is set to English (United States), Word may ignore that entry. You can either change the dictionary language or update the proofing language for the affected text from Review > Language > Set Proofing Language.
Use a shared custom dictionary
Teams can use a shared dictionary to standardize spellings for brand names, internal tools, acronyms, and client terminology. Place the dictionary file in a shared location, then use Add in the Custom Dictionaries window to connect it. If several people need to update it, make sure they have permission to edit the file. If users should only apply the approved spellings, provide read-only access so Word can use the dictionary without allowing accidental changes.
Add Multiple Words to a Custom Dictionary File
If you have a long list of names, product terms, abbreviations, technical phrases, or industry-specific words, adding them one at a time in Word 365 can be slow. A faster method is to edit the custom dictionary file directly. Word custom dictionaries usually use the .dic file format, and the main custom dictionary is often named CUSTOM.DIC. Each accepted spelling is stored as plain text, usually with one word per line.
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1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesBefore editing the file, close Microsoft Word to reduce the chance of the dictionary being locked or overwritten. Then locate the dictionary file through Word’s settings. Open Word, go to File > Options > Proofing, select Custom Dictionaries, choose the dictionary you want to update, and look at the path shown in the dialog box. You can select the dictionary and choose Edit Word List for small changes, but for bulk additions, use the file location so you can open the dictionary in a text editor such as pad.
- Close Word 365 and any other Office apps that may be using spelling tools.
- Open File Explorer and go to the folder shown in the Custom Dictionaries window.
- Make a backup copy of the dictionary file before changing it.
- Right-click the .dic file and open it with a plain text editor.
- Add each new word on its own line.
- Save the file as plain text, keeping the original .dic extension.
- Reopen Word and test one or two of the added words in a document.
Use a simple format when adding entries. Do not separate words with commas, tabs, or semicolons unless those characters are actually part of the term you want Word to recognize. For example, a dictionary file for a company might include entries like this:
- ContosoCloud
- NorthwindAI
- Q4Roadmap
- MacDonaldson
- eDiscovery
Word’s spelling dictionary is best suited to single words, names, acronyms, and terms without spaces. If you need Word to recognize a multi-word phrase, such as a department name or product slogan, the spelling dictionary may not behave the way you expect. In that case, consider using AutoCorrect, AutoText, or the grammar and style settings instead. For hyphenated terms, add the exact form you use most often, such as client-facing or zero-trust.
Be careful with capitalization. Depending on the dictionary language and proofing behavior, Word may treat different capitalized forms differently. If a term is commonly used in more than one form, add the versions you actually want accepted, such as PowerShell and powershell only if both are acceptable in your documents. Also make sure you are editing the custom dictionary assigned to the correct language. A word added to an English United States dictionary may not be accepted while proofreading a paragraph marked as English United Kingdom, French, Spanish, or another language.
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For shared terminology in a team environment, create a separate custom dictionary instead of overloading your personal CUSTOM.DIC. You can place the shared .dic file in a synced or network location, then add it through Custom Dictionaries in Word. This makes it easier to update company vocabulary, remove outdated terms, and keep spelling behavior consistent across users who work with the same documents.
Remove or Edit Words You Added by Mistake
If you accidentally add a misspelled word to the Word 365 dictionary, Word may stop flagging it as an error in future documents. To fix this, remove the incorrect entry from the custom dictionary that stored it. This is also useful when a product name, person’s name, or internal term changes and you want Word to recognize only the updated spelling.
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Start by opening the custom dictionary list in Word. On Windows, select File > Options > Proofing, then choose Custom Dictionaries. Select the dictionary that contains the word, usually CUSTOM.DIC, and click Edit Word List. In the word list, select the unwanted entry and click Delete. If you want to replace it with a corrected spelling, type the corrected word in the Word(s) box and click Add, then confirm with OK.
On Mac, open Word and go to Word > Preferences > Spelling & Grammar. Look for the custom dictionary controls, then open the relevant dictionary or word list. Remove the incorrect word, add the corrected version if needed, and save your changes. The exact labels can vary slightly by Word 365 build, but the process is the same: find the custom dictionary, edit its word list, and remove the mistaken entry.
What to check before deleting a word
- Correct dictionary: If you use more than one custom dictionary, the word may not be in the first one you open.
- Language setting: Custom dictionaries can be tied to a language. A word added under English (United States) may not apply to English (United Kingdom).
- Capitalization: Some entries may be treated differently if they were added with uppercase letters, lowercase letters, or mixed case.
- Shared dictionaries: If the dictionary is stored on a network or managed by an organization, you may not have permission to edit it.
After deleting or correcting the entry, close and reopen the affected document if Word continues to accept the old spelling. You can also run a fresh spell check by selecting Review > Spelling & Grammar. If the misspelled word still is not flagged, make sure the text has not been set to Do not check spelling or grammar. Select the text, go to Review > Language > Set Proofing Language, and clear that option if it is enabled.
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If you add a word to the dictionary in Word 365 and it is still underlined later, the issue is usually tied to the active proofing language, the selected custom dictionary, file permissions, or a cloud/account sync problem. Start by testing the word in a new blank document. Type the custom word, right-click it, and check whether Add to Dictionary is available. If the command is missing or greyed out, Word may not have a writable custom dictionary selected.
Check the proofing language
Custom dictionaries can be linked to specific languages. A word added while the text is marked as English United States may still be flagged if the same word appears in text marked as English United Kingdom, French, Spanish, or another proofing language. Select the affected word or paragraph, go to Review > Language > Set Proofing Language, and confirm that the correct language is selected. Also make sure Do not check spelling or grammar is not selected unless you intentionally want Word to ignore that text.
Confirm that the custom dictionary is enabled
Open File > Options > Proofing, then choose Custom Dictionaries. In the list, confirm that your dictionary, often named CUSTOM.DIC, has a check mark beside it. Select it and review the Dictionary language setting. If it is set to a language that does not match your document, either change the language setting where appropriate or create a separate dictionary for that language.
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- Wrong default dictionary: select the dictionary you want and choose Change Default.
- Wrong language: set the dictionary to All Languages or to the same language used in the document.
- Dictionary not listed: use Add to browse to the custom dictionary file, then enable it.
Make sure Word can write to the dictionary file
If Word accepts the word during the session but forgets it after closing and reopening, the dictionary file may be read-only or stored in a protected location. In the Custom Dictionaries window, select the dictionary and look at the file path. Close Word, then open that folder in File Explorer. Right-click the dictionary file, choose Properties, and clear Read-only if it is selected. If the file is stored in a restricted network folder, OneDrive folder with sync issues, or a location controlled by your organization, copy it to a local user folder and add it again through Word’s custom dictionary settings.
Repair common Word 365 dictionary glitches
If the settings look correct but the word still will not save, close all Office apps and reopen Word. Then try adding the word again. For persistent issues, sign out of your Microsoft 365 account in Word, sign back in, and let Office finish syncing. You can also run an Office repair from Windows by opening Settings > Apps > Installed apps, selecting Microsoft 365, choosing Modify, and running Quick Repair. If that does not help, run Online Repair.
In managed work or school installations, administrators may block changes to proofing tools or redirect dictionary files to a controlled location. If the custom dictionary keeps resetting, test with a local document outside SharePoint or OneDrive, then contact your Microsoft 365 administrator if the behavior continues. Once the correct language, enabled dictionary, and writable file location are in place, Word 365 should stop marking your custom terms as spelling errors.
Frequently Asked Questions
Where is the Add to Dictionary option in Word 365?
Type the word in a document, then right-click the word while it is underlined as a spelling error. If Word recognizes it as a possible custom word, you should see Add to Dictionary in the menu. If the option is missing or grayed out, check that spell check is enabled and that a writable custom dictionary is selected in Word’s proofing settings.
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Open Word’s custom dictionary settings, select the dictionary you want to use, and choose the option to edit the word list. You can add words individually there, or open the custom dictionary file in a text editor and paste mulle words, with one word on each line. Save the file, then restart Word if the new words are not recognized immediately.
Can I remove a word I accidentally added to the dictionary?
Yes. Go to Word’s proofing settings, open Custom Dictionaries, select the dictionary that contains the word, and edit the word list. Find the incorrect entry, delete it, and save the change so Word starts flagging that spelling again.
Why does Word 365 still mark a word as misspelled after I added it?
This usually happens when the word was added to a different custom dictionary, the dictionary is not enabled, or the document is using a different proofing language. Check File > Options > Proofing > Custom Dictionaries and confirm the correct dictionary is checked. Also select the text and verify that the language matches the dictionary you are using.
Does adding a word to the dictionary in Word 365 also add it to Outlook or other Office apps?
Often, yes, because Microsoft Office apps can share the same custom dictionary file. If Outlook, PowerPoint, or Excel is using the same enabled custom dictionary, the word should stop being flagged there too. If it does not, check that app’s proofing settings and confirm it is pointing to the same custom dictionary.
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Bottom Line
Adding words to the Word 365 dictionary is usually as simple as right-clicking the flagged term and choosing to add it, but the Proofing settings and Custom Dictionaries menu give you more control when you need to manage many terms or use a shared dictionary.
If a word still shows as misspelled, check that the correct custom dictionary is enabled, the proofing language matches your document, and Word has been restarted after changes. Once set up properly, custom dictionaries can save time and keep specialized names, terms, and abbreviations from interrupting your writing.
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