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DAX parameter-naming conventions

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Parameter names are standardized in DAX reference to facilitate the usage and understanding of the functions.

Parameter names

Term Definition
expression Any DAX expression that returns a single scalar value, where the expression is to be evaluated multiple times (for each row/context).
value Any DAX expression that returns a single scalar value where the expression is to be evaluated exactly once before all other operations.
table Any DAX expression that returns a table of data.
tableName The name of an existing table using standard DAX syntax. It cannot be an expression.
columnName The name of an existing column using standard DAX syntax, usually fully qualified. It cannot be an expression.
name A string constant that will be used to provide the name of a new object.
order An enumeration used to determine the sort order.
ties An enumeration used to determine the handling of tie values.
type An enumeration used to determine the data type for PathItem and PathItemReverse.

Prefixing parameter names or using the prefix only

Term Definition
prefixing Parameter names may be further qualified with a prefix that is descriptive of how the argument is used and to avoid ambiguous reading of the parameters. For example:

Result_ColumnName - Refers to an existing column used to get the result values in the LOOKUPVALUE() function.

Search_ColumnName - Refers to an existing column used to search for a value in the LOOKUPVALUE() function.
omitting Parameter names will be omitted if the prefix is clear enough to describe the parameter.

For example, instead of having the following syntax DATE (Year_Value, Month_Value, Day_Value) it is clearer for the user to read DATE (Year, Month, Day); repeating three times the suffix value does not add anything to a better comprehension of the function and it clutters the reading unnecessarily.

However, if the prefixed parameter is Year_columnName then the parameter name and the prefix will stay to make sure the user understands that the parameter requires a reference to an existing column of Years.