Plain definition
Trend analysis compares the same defined measure over time to identify direction, seasonality, or a change in rate. It describes a pattern; it does not establish its cause.
Illustrative example
Gross margin falls from 36% to 34%, then 31% over three months. Revenue is rising, so management investigates product mix, supplier price, and discount approvals before declaring a pricing problem. A year-ago comparison is added because the business has a seasonal promotion.
Why it matters
A trend can reveal a deterioration early, but acting on it without checking the underlying change can misallocate resources. The value is a focused question about what shifted and whether it will continue.
Practical consequence
Use consistent definitions and comparable periods, display both amount and rate where needed, and investigate a material change with the underlying transaction or operating data.