덩달다 (deong-dal-da) – follow suit/do the same as (someone)
This word is usually used to describe how a person would in a way have the same feelings/opinion about something, therefore doing the same action as another person.
It can also be used to describe how inanimate objects like costs and expenses move in tandem with each other.
The key point here is to understand 덩달다 is used to describe things that happen “in tandem”.
우리 엄마의 생신 파티 할 때 모두 부끄러워서 나 먼저 생일 노래를 부르고 다들도 덩달아 불렀어.
During my Mom’s birthday party, everyone was shy so I started singing the birthday song first and everyone else followed suit.
경제성장은 올라가면 생활비용도 덩달아 올라가서 돈을 많이 아껴야 하지.
When economic growth increases, living expenses will follow suit and increase too so we have to be thrify with our money.