A family of Microsoft word processing software products for creating web, email, and print documents.
The AutoCorrect feature in Word doesn't work that way. It makes a change only after you press the spacebar or a punctuation character. If you don't type one of those keys, even if the part of the word is a "trigger" for an AutoCorrect item, Word will sit and wait for the next keypress that signals the end of the word.
What you're describing is "predictive text", which is a different feature. To turn it off, go to File > Options > Advanced and clear the check box for "Show text predictions while typing".
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A quick way to get there is to click the Text Predictions section of the status bar at the bottom of the Word window (assuming you have that section turned on in the right-click menu of the status bar).
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More info at https://www.howtogeek.com/726539/how-to-use-text-predictions-in-microsoft-word/