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nlpbleu

Difference between adequacy and fluency in ngram

"When 1-gram precision is high, the reference tends to satisfy adequacy.

When longer n-gram precision is high, the reference tends to account for fluency."

What does this mean?

Solution

  • Adequacy: How much of the source information is preserved?

    Fluency: How good is the generated target language quality?

    For Machine Translation task,

    English(S-V-O): A dog chased a cat

    Reference translation in Hindi would look like:

    Hindi(S-O-V): A dog a cat chased

    When 1-gram precision is high, correct word-to-word translations will be high but order of those words might not be correct in translated sentence. But still, majority of the source information is preserved.

    High 1-gram, low N-gram(2-gram) precision value example: chased dog cat

    When N-gram precision is high, order of those words will be preserved to some extent and you would get a fluent sentence in Hindi.

    High N-gram(2-gram) precision example: A dog cat chased