Rest and quietness — keeping calm and inactive to recover, especially used in medical contexts for illness or injury.
医者に安静にして、一週間は安静が必要だと言われた。
The doctor told me to rest; I need to keep quiet for a week.
出産後は十分な安静と栄養が大切だ。
After giving birth, sufficient rest and nutrition are important.
骨折した場合は患部を安静にしておく必要がある。
In case of a fracture, you need to keep the injured area at rest.