The lead investor is the investor that contributes the largest portion of the investment. They play an important part in the development of a business, for it is usually they who sign the Term Sheet and engage in the seed investment.
Lead investors can be family members or friends of the business founder, high-net individuals (ie angel investors) or venture capital investors. Any other investors (ie those who contribute a smaller proportion of the investment than the lead investor) are referred to as ‘additional investors’ or simply ‘investors’.
For more information, read Funding your business and Startup funding.