Definition
A lot is the unit of sale in an auction. A lot can be a single item (Lot 142: 1956 Topps Mickey Mantle PSA 8) or a group of items sold together (Lot 78: collection of 25 signed 1970s baseball cards). Lots are catalogued with descriptions, photographs, condition reports, and estimates.
Why it matters
How an item is grouped into lots can change its realized price significantly. Auction houses make these decisions; consignors should ask in advance.
Example
At a sports memorabilia auction, Lot 41 is described as "Single-signed Babe Ruth official AL ball, PSA/DNA Authentic, w/ provenance from estate of [collector name]." The lot includes an estimate of $25,000–$35,000.