Remove all words that DOESN'T contain a colon

Question

I have a file with this type of lines:

blabla bla:bla whatever what:ever
alpha bravo charlie
del:ta

I only want to keep the words that contain a colon.

So the output for the above would be:

bla:bla what:ever

del:ta

Does anyone have any ideas?

Answer 1

grep -oE '\w+\:\w+' filename.txt