A single value for column 'X' in table 'Y' cannot be determined.

A measure or calculated column referenced a bare column that has many rows in the current context, but DAX needs exactly one value.

Why it happens

• A measure refers to a column without an aggregation (e.g. = Sales[Amount] instead of SUM(Sales[Amount])).
• A calculated column reaches a column on the many-side of a relationship without RELATED or an iterator.
• A column is used where a scalar is expected and the current filter/row context leaves more than one row visible.

How to fix it

1. Wrap the column in an aggregation: SUM, MAX, MIN, AVERAGE, or COUNT.
2. If you genuinely expect one value, use SELECTEDVALUE(Table[Column]) — it returns BLANK instead of erroring when several remain.
3. In a calculated column reaching another table, use RELATED (to the one-side) or an iterator like SUMX (to the many-side).

Revenue = Sales[Amount]

Revenue = SUM ( Sales[Amount] )