～たことがある

About

～たことがある indicates that one has had a certain experience, and is a combination of a past casual form verb, こと, the が particle, and ある.

It is also possible to form a negative version of ～たことがある by conjugating ある to ない, or the polite ありません. The affirmative may also be made polite by conjugating to あります.

ある may also be conjugated into the past tense as あった or ありました. This makes it seem as though you are viewing your past experience from the point of view of your past self (i.e. "I had had X experience (at the time).").

～たことはある, is also possible, and only differs in nuance: the は particle emphasizes what comes after, and creates a sense of contrast. E.g. "I have done that, (but...)."

In casual speech, the が particle is often dropped (～たことある).

Summary

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  Combine ことがある with a past casual verb to express that you've had a given experience

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  ある may be conjugated into the negative or past tense

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  ～ことはある and ことある are also possible