Syntax for using variables in a range

Hello, i am trying to copy a range of cells to the cells beneath it and then do the same down to the last row but i can't seem to get the syntax for it. i know to select one cell using a variable is:

Range("a" & i).Select
but
Range("a" & i:"d" & i).Select doesn't

if somenone could correct my ignorance i would be most thankful.

Regards,
Bill Mahoney
New York, NY