noun
lessons; classes; practice (of an art or skill)
Refers to structured learning of a non-academic skill, such as music, dance, calligraphy, or martial arts, often as a regular extracurricular activity.
娘は週に二回、ピアノの習い事に通っている。
My daughter goes to piano lessons twice a week.
When I was a child, I took calligraphy as an extracurricular lesson.