It is more strategic to include the plural version of keywords than the singular form when performing SEO keyword research. Plurals provide greater flexibility and more opportunity for search traffic. Search algorithms have evolved and become more sophisticated. Now, they are able to index more than the specific words, but also the roots of these words.
This is why it is important to always prefer longer words. Adding suffixes or plurals to targeted terms is recommended. The concept of “rooting” is relatively new to the SEO world, but it cannot be ignored. The increase in potential search traffic may surprise you.
An example would be to optimize for “contracts” or “contracting”, instead of just “contract”. The latter term is contained within the former two terms. In other words, if you are optimizing for “contracts” or “contracting”, you are already optimizing for “contract” by default. Be sure to consider this strategy when doing your keyword research and integrating your targeted terms.