.. terminal. no sudoers found

MacMini OS 10.9.5 FireFox

Whenever I attempt to do anything that requires 'sudo' authority I am returned with the following message, as an example.

sudo: unable to stat /etc/sudoers: Permission denied

sudo: no valid sudoers sources found, quitting

I don't read or write code. I don't get into the guts of the terminal or OSX, however there are any number of times I need to issue, or paste a Terminal command as a sudo.

I am at a loss.

questions, comments, suggestions, all welcome.