Did Eru have physical form?

I've been reading up on the creation of Arda through Iluvatar and his Music (side note, must recommend The Encyclopedia of Arda as a great resource, in addition to Barrow Downs of course). There seems to be no reference to any physical form that Eru might have taken or been described as. Although I'm not a scholar of the Silmarillion or anything, I was just curious if Tolkien ever described what Eru might look like to the people of Middle Earth. Did they envision him as having human form or something completely different? Thanks.