sternly
adverbUK /ˈstɜːnli/
US /ˈstɜːrnli/
In a serious and strict way that shows you are not joking.
The teacher spoke sternly to the children who were running in the hall.
OTHER MEANINGS
2. In a way that shows strong disapproval.
She looked sternly at her brother when he told a lie.
3. With a harsh or unsmiling manner.
The guard nodded sternly and pointed to the exit.
4. In a way that demands obedience and leaves no room for argument.
The coach sternly told the team to be on time.