Factors is a 3rd person present and a plural noun for a word "FACTOR."
1. A circumstance, fact, or influence that contributes to a result.
2. A number or quantity that when multiplied with another produces a given number or expression.
3. A level on a scale of measurement.
4. (Of a company) sell (its invoices) to a factor.
A number of factors contributed to the plummet of the Irish population.