People from different places use different words for things, even everyday things such as carbonated beverages (e.g. soda, coke, pop) or bread roll-based sandwiches (e.g. hoagie, grinder, sub). Regional variation in vocabulary is one of the foci of dialectology, a subfield of linguistics that examines the geographic distribution of specific words, along with distributions of different pronunciations and grammatical constructions. This Element will provide readers with a basic understanding of traditional dialectological study and will demonstrate through examples (audio, text, maps) how Linguistic Atlas Project research has changed and expanded over time. Readers will be introduced to the key concepts of dialectology with a focus on the North American Linguistic Atlas Project (LAP) and its materials. This Element will also discuss today's LAP with reference to third-wave sociolinguistics, outlining the ways in which the LAP has changed over time to meet the needs and goals of contemporary sociolinguistic study.