yes, log in and log out doesn't effect ur search history and saved words .....but if u'll uninstall it then u lose ur data including word of the day.....i advise u to subscribe this app's web page on Google 2 get words of the day without installing it.
@Israil lashkare have you tried!?
@shabana saifi my query is whether my saved words are always synced with my account or not so that I can login/out freely?