The above is a potential pattern. The potential covers two different situations in which (1) one possesses the ability to do something, for instance, skill in foreign languages, sports, driving, and cooking; and (2) one is allowed to do something under the circumstances, for instance: りゅう学生は りょうに 入る ことが できます(International students can live in the residence hall), and お金が ないから、本を 買う ことが できません(I can't buy books because I have no money).
マリアさんは ピアノを ひく ことが できます。
Maria can play the piano.
りゅう学生は この りょうに 入る ことが できます。
International students can live in this dormitory.
もう いちど 日本へ 来る ことが できますか。
Is it possible for you to come to Japan again?
