I have difficulty in understanding this concept.

His comment was tongue in cheek.

The amount of time spent on a task should be in proportion to its importance.

The product is currently in-process.

I slowly poured in the cream to make the batter smooth.

The once thriving town was left in shambles after the hurricane.

In this vein, I believe we should continue our efforts to improve the education system.

In my day , smartphones weren't even a thing .

In truth, I have never been to Japan.

He forgot to lock in his car and it got stolen.