"What's the unit?" The answer to this question makes all the difference. A young child who is asked to count shoes needs to know if the unit to be counted is "pairs" of shoes or individual shoes. A middle school student who is asked for the length of a table will want to know if the number should be in inches, feet, or meters. The importance of the unit is cited as early as prekindergarten as an essential understanding, Big Idea 2a, "Using numbers to describe relationships between or among quantities depends on identifying a unit" (Dougherty et al. 2010, p. 8). Judging whether an answer is expressed in the appropriate unit is also cited as a key element of reasoning and sense making and is considered foundational for high school (NCTM 2009, p. 21). Mistakes stemming from not attending to the unit are common. A case in point is a sign found at a bakery that indicates coffee and donuts are sold for ".95 cents." Is ".95 cents" the same as "$.95"? Over half of students will respond incorrectly to this question. This article presents an example of why paying attention to the unit under discussion makes all the difference. Because advertisements like the one at the bakery window are not uncommon, teachers must be careful to discuss with students the proper use of units. Students should expect their answers to make sense and recognize errors when they see them in advertisements.