function pluralize(phrasePropositions, pluralForm) {
  var isPluralizable = Array.isArray(phrasePropositions) && Number.isInteger(pluralForm);

  if (isPluralizable) {
    return phrasePropositions[pluralForm];
  }

  return phrasePropositions;
}
Try to choose plural form from available phrase propositions.

@param {Array} phrasePropositions List of phrases propositions.
@param {number} pluralForm Number determining which phrase form should be used.

@returns {String|Array} One particular phrase if it's possible, list of unchanged phrase propositions otherwise.