Replace comma with newline

Hi, for some reason I cant seem to figure this out. I have a file which looks something like this

word
word
word
word
word,word,word
word
word
word,word,word,word,word
word
word

Basically I want this whole thing to be a list with 1 word on each line like this...

word
word
word
word
word
.
.
.

So my plan of attach was to use sed to replace the comma (,) with a newline like so:

sed 's/,/\n/g'

Which basically added a "n" where the comma was formerly. Any idea on how I can achieve my desired result? Thanks!

tr -s ',' '\n' < oldfile > newfile