Jisho.org Forum

これは猫だから。- Because it's a cat.
だから、行きます。- That's why (some reason has to be stated before) I'll go.
彼が日本からです。- He's from Japan.
これからです。- From this (...)

Oh, and by the way.
からだ is also a reading for 体 (body).

Thanks for replying, but I've seen からだ used to mean 'because/since', not just 'from'.

At first I thought some people preferred using からだ to 体, but then I took the time to translate the sentences and found out that they meant からだ in the explanatory sense.

Take these sentences for example:
死が目に見えぬものであるからだ (Because our eyes are unable to see death.)
誰もこの話を信じないだろうからだ (That's because I don't suppose anybody will believe this story.)
私が彼が嫌いなのは彼が残酷だからだ (It is because he is cruel that I dislike him.)

Use of 「だ」is optional.

これは猫だから。- Because it's a cat.
これは猫だからだ。- Because it's a cat.
これは猫だからです。- Because it's a cat.

Oh, I see. That's interesting. Thank you. (:

Is there a difference in politeness level if you say これは猫だからです instead of これは猫ですから or are they the same?

Politeness is same.