Probably not news to ClaireBear, but some others may not realize that in Word one has not only the spellcheck dictionary, which can be changed by swapping languages, but also a Grammar check and AutoCorrect and Autoreplace functions.

It's helpful to know in what order things happen with respect to these functions.

The base spellcheck dictionary cannot be modified, so you can't delete words from it. You can add words to your own "custom dictionary" if you find ones that are not in the dictionary.

Spellcheck runs first, so if there's a word that is in the spellcheck dictionary that you don't want, you "delete" it by entering, in the AutoCorrect dictionary, the "correctly spelled" word that spellcheck inserts, so that after Spellcheck inserts the word, AutoCorrect replaces it with the word you want. Replace "tire" with "tyre," as an example.

AutoCorrect also "trumps" (comes after) the Grammar check and AutoFormat, so that if you allow the program to "correct initial caps," which changes TOP SECRET to Top Secret, entering a Change "Top Secret" to "TOP SECRET" in AutoCorrect lets you automatically change it back to "TOP SECRET" after SpellCheck and AutoFormat both think they've fixed it. This can be really handy with some company names (especially Brit ones) that have formats like xXxXXXx ('cause it's cute).

This is also how one eliminates the need to use WordImPerfect in order to get their "legal spellcheck dictionary"¹ that deletes "trail" from the spelling dictionary. Just enter in AutoCorrect: "trail" to "trial."

¹ The only known sem-rational reason for adoption of WierdPerfect by nearly all legal firms a couple of decades ago.

John