What it means
ことがある has two common uses. After a verb in the ta-form, it means that someone has experienced doing something at least once before. After a verb in the dictionary form, it means that something sometimes happens or that there are occasions when someone does something. The expression is neutral and can be used in both familiar and polite sentences.
Usage note
The verb form changes the meaning: ta-form + ことがある refers to past experience, while dictionary-form + ことがある describes an occasional event. Do not confuse this expression with ことができる, which means that someone can do something.
How to use it
Verb (dictionary form)ことがあります
冬は雪が降ることがあります。
It sometimes snows in winter.
Verb (た-form)ことがあります
京都へ行ったことがあります。
I have been to Kyoto before.
Verb (dictionary form)ことがある
冬は雪が降ることがある。
It sometimes snows in winter.
Verb (た-form)ことがある
京都へ行ったことがある。
I have been to Kyoto before.