事(こと)があるSomething is possible, Sometimes, Occasionally, There are times when

ことがある is an expression in Japanese that combines the noun こと with the case marking particle が, and the う - Verb, ある. It is often translated as 'to be possible', 'to occasionally occur', or 'to sometimes occur'. However, the more literal translation of ことがある is '(A) is a thing that exists'.

ことがある may be paired with the attributive form of any other word.

Occasionally, が may be replaced by も. In these situations, it implies that '(A) is also a thing that exists'. Basically this just highlights that (A) is something that needs to be considered (among other things).

Caution

ことがある differs from たことがある (a phrase commonly paired with the past form of verbs). たことがある highlights a single event in which the (A) verb was completed. However, when the verb is not in past form, it simply implies that there are 'times' when the verb happens, as opposed to a single/specific time.