Analysis
Metric
Also called measure.
Metric is a number the system derives by summing, averaging, or rating events. Every figure on a report is one.
How it is measured
A metric has a name, a unit, an aggregation, and a scope. Sessions, bounce rate, and average load time are all metrics, each with its own rule for what goes into the count.
Always read the definition next to the name. Two tools can both show 'users' and count different things. Check the unit, the window, and the filters.
Worked example
A garden-centre site has a 'visitors' number of 12,600 in its analytics and 9,100 in its email platform's click report. Neither is wrong.
The analytics tool counts distinct visitors in a window, while the email tool counts unique clickers who then loaded a page. The owner renames the report column to 'distinct visitors, 28 days' so the two stop competing.
How it differs
A metric is a measured quantity. A dimension is the attribute used to break it down. Together they form a report: metric in the cells, dimension down the side.
Common errors
Comparing numbers with different definitions. Reading a name and assuming the rule. Forgetting units. Mixing a total and an average in one chart. Not noting the window.
In practice
Pick the five metrics you quote most and write down the exact rule for each. Put the definition in the report footer. Share it before the next meeting.