1. A process undertaken by states to certify that a given voter system is acceptable for use. In principle, only certified systems may be used in an election, although the reality is sometimes at variance with this requirement.

Source: Asking the Right Questions about Electronic Voting Asking the Right Questions about Electronic Voting, National Research Council on the National Academies, https://www.nap.edu/catalog/11449/asking-the-right-questions-about-electronic-voting

2. Procedure by which a third party gives written assurance that a product, process or service conforms to specified requirements.

Source: Glossary of terms database, U.S. Election Assistance Commission, https://www.eac.gov/glossary/

3. Certification is the point in the election process at which the vote count is finalized and made official. There are generally two stages of the certification process for statewide elections: first, the local election jurisdiction certifies the vote count to the state, and second, the state certifies the final vote count.

Source: ELECTIONS: The Nation’s Evolving Election System as Reflected in the November 2004 General Election, U.S. Government Accountability Office, https://www.gao.gov/assets/160/157713.pdf