丁寧語
the丁寧語 of the copula is でございます. Note that this is just で + 御座います, the 丁寧語 form of ある.
お釣りでございます Here is your change change (money)
Omitting is feminine
afeminine speech pattern is to omit the copula. 「寿司だ（よ）ね」→「寿司ね」
Recall
with 〜た, can be used to denote that you recall something or that you have noticed something
図書館があるんだった I remember that there is a library
この文章は中国語だった I've noticed that this sentence is in Chinese.
日本は寒いんでした I can recall that Japan is cold.