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Out Of Vocabulary In NLP

This article explains the term out of vocabulary (OoV) in NLP.

What Is Out Of Vocabulary?

Out-of-Vocabulary (OOV) is an NLP term for words that appear in your input text but were not seen during the model’s training (or vocabulary creation) phase.

Example

Suppose you train a model on these sentences:

“I love apples”
“I love bananas”

Your vocabulary becomes:

{I, love, apples, bananas}

Here:

I → in vocabulary
love → in vocabulary
mangoes → Out-of-Vocabulary (OOV)

Posted By -	Karan Gupta

Posted On -	Wednesday, February 11, 2026

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