The correct answer is "precinct." To determine this, one can either recall prior knowledge on the topic or conduct a search online. In this case, a simple search using a search engine like Google can provide the answer. One can simply enter the query "What is another term for election districts?" or "What is the term used for the geographic unit where voters are assigned on election day?" The search results would likely list "precinct" as one of the terms used to refer to these election districts. Therefore, based on the search results or prior knowledge, the correct answer would be "precinct."