Humanizr/Humanizer · error · ArgumentException

Unrecognized number word

Error message

Unrecognized number word: {unrecognizedWord}

What it means

This ArgumentException is thrown by LinkedVigesimalWordsToNumberConverter.Convert (the throwing entry point) when TryConvert returns false. This converter handles linked-vigesimal number words where scale nouns appear before their count words (e.g. Welsh, Breton, Irish style). The error fires when the input phrase contains a token that cannot be matched as an exact word, ordinal, scale name, scale count, or terminal remainder joiner. The unrecognized word or full input is included in the message.

Solutions

1. Use TryToNumber(words, out value, culture, out unrecognizedWord) for user-facing or untrusted input.
2. Verify the input phrase follows the locale's grammar: scale noun, then count, optionally joined by a remainder word.
3. Inspect the unrecognizedWord to locate the first unmatched token.
4. Ensure the culture matches the language of the words and that the locale has full vocabulary coverage.

Example fix

// before
long value = phrase.ToNumber(new CultureInfo("cy"));

// after
if (!phrase.TryToNumber(out var value, new CultureInfo("cy"), out var bad))
    Console.WriteLine($"Unrecognized: {bad}");

bool canParse = words.TryToNumber(out var value, culture, out var unrecognized);
if (!canParse)
    Console.WriteLine($"Unrecognized: {unrecognized}");

static bool LooksLikeNumberWords(string words, CultureInfo culture) =>
    !string.IsNullOrWhiteSpace(words) && words.TryToNumber(out _, culture, out _);

try
{
    return words.ToNumber(new CultureInfo("cy"));
}
catch (ArgumentException ex) when (ex.Message.Contains("Unrecognized number word"))
{
    return 0;
}

When it happens

Trigger: Calling "words".ToNumber(culture) for a linked-vigesimal locale with a phrase containing a token not in the locale's exact-words dictionary, ordinal map, or scale vocabulary, or a phrase whose structure does not match the scale-noun-before-count grammar.

Common situations: Free-text user input with misspellings or words from a different language; locale mismatch; ordinal phrases not authored in the locale's ordinal map; scale count words outside the locale's range; input with Unicode or diacritic differences the normalizer does not handle; phrases where the terminal remainder joiner is missing or incorrect.

Related errors

• Unrecognized number word
• Unrecognized number word
• Unrecognized number word
• Unrecognized number word
• Unrecognized number word

AI-assisted analysis of Humanizr/Humanizer@ffc2b77c0f (2026-08-13). Data as JSON: /api/errors/3e5a7d0b800a9e65. Report an issue: GitHub.

Appendix: source

Thrown at src/Humanizer/Localisation/WordsToNumber/LinkedVigesimalWordsToNumberConverter.cs:15

namespace Humanizer;

/// <summary>
/// Parses linked-vigesimal words with scale nouns before their count words.
/// </summary>
internal class LinkedVigesimalWordsToNumberConverter(LinkedVigesimalWordsToNumberProfile profile) : GenderlessWordsToNumberConverter
{
    readonly LinkedVigesimalWordsToNumberProfile profile = profile;

    /// <inheritdoc />
    public override long Convert(string words)
    {
        if (!TryConvert(words, out var parsedValue, out var unrecognizedWord))
        {
            throw new ArgumentException($"Unrecognized number word: {unrecognizedWord}");
        }

        return parsedValue;
    }

    /// <inheritdoc />
    public override bool TryConvert(string words, out long parsedValue) =>
        TryConvert(words, out parsedValue, out _);

    /// <inheritdoc />
    public override bool TryConvert(string words, out long parsedValue, out string? unrecognizedWord)
    {
        if (string.IsNullOrWhiteSpace(words))
        {
            parsedValue = default;
            unrecognizedWord = words ?? string.Empty;
            return false;
        }

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