Represents a word combination in the context of relevant words.

@constructor

@param {string[]} words The list of words that this combination consists of.
@param {number} [occurrences] The number of occurrences, defaults to 0.
@param {Function} functionWords The function containing the lists of function words.
function WordCombination( words, occurrences, functionWords ) {
	this._words = words;
	this._length = words.length;
	this._occurrences = occurrences || 0;
	this._functionWords = functionWords;
}