What is data granularity in a data warehouse?

Granularity refers to the level of detail or summarization in the units of in the data warehouse (Inmon, WH 2002). For example, one of the dimension might be a date/time dimension which could be at the year, month, quarter, period, week, day, hour, minute, second, hundredths of seconds level of granularity. High granularity means that the data is at or near the transaction level, which has more detail. Low granularity means that the data is aggregated, which has less detail.