A common or everyday occurrence; something that is not unusual.
失敗するのはよくあることだから、あまり気にしないで。
Failing is a common thing, so don't worry too much.
電車が遅れるのは都会ではよくあることだ。
Train delays are a common occurrence in the city.
彼との意見の食い違いはよくあることだから、冷静に話し合おう。
Disagreements with him are common, so let's discuss it calmly.