To take a more abstract example, when we learn a word such as week or weekend, we are inheriting a conceptual system that operates with amounts of time as common categories. Having words for units of time such as “two days” or “seven days” shows that we can think of time (i.e. something abstract) in amounts, using noun phrases, in the same way as “two people” or “seven books” (i.e. something physical). In another world view, time may not be treated in this way. In the Hopi language, spoken in Arizona, there were traditionally no terms equivalent to most of our time words and phrases (two hours, thirty minutes) because our terms express concepts from a culture operating on “clock time.” Perhaps for a similar reason there was no term for a unit of seven days. There was no “week,” nor was there a term for “Saturday and Sunday” combined as a unit of time. There was no “weekend.”