0 - 3 of 3 tags for median

I have a database table which has four columns and two of the columns are INT. The two INT columns' rows are sometimes empty.
When I try to cast them as DECIMAL(18,3) and then use the Median function I am getting the Error: An unknown character string translation was requested.
 

If I type median in a Teradata query, the word becomes blue, but it does not become bold and blue.
So, I suspect what's going on is that median is not, in fact, a function in Teradata, but the word is reserved and cannot, for example, be assigned to a user written function. Is this correct?

In my previous posts on missing functions i covered SQL:2008 DENSE_RANK and CUME_DIST & NTILE.