1. ordinary; common; usual
さっきのはただの冗談だったのに。That earlier one was just a joke.
2. free of charge; free
esp. 只 if written with kanji
ただでもらったチケットだ。It's a ticket I got for free.
3. unaffected; as is; safe
usu. as ～では...
4. only; merely; just; simply
少年は、ただ母と一緒にいたかったのだ。The boy simply wanted to be with his mother.
5. but; however; nevertheless; except
esp. 但 if written with kanji
ただ、一つだけ確認しておきたいことがあるのです。However, there is just one thing I would like to confirm.