～ので
You can use ので to give the reason for the situation described in the sentence. ので acts much in the same way as から but it sounds slightly more formal. The reason part of the sentence ends in a short form predicate. When ので follows a noun or a なadjective, な comes in between.
いつもにほんごではなすので、にほんごがじょうずになりました。
My Japanese has improved because I always speak Japanese.
きょうはにちようびなので、ぎんこうはやすみです。
Banks are closed, because today is a Sunday.