i want to print following using awk

Hi all
I have taken input

$fname=filename.345.txt

Now i want to awk with using delimiter as '.' and print last word. i.e in this case it is "txt". I have tired like this

echo $filename | awk -F"." '{print $END}'

but it is not working. Can any one help me

Thank U
Naree

echo "filename.345.txt" | awk -F'.' '{ print $NF }'

Dear Robot

 Thanks a Lot!!! Supereb!!!