調整 and 調節

Question about Japanese
What is the difference between 調整 and 調節?


Answer:
I hope the following example will help you understand the difference between 調整 and 調節.

The meanings of 調整 and 調節 are very close. I looked up both words in a dictionary, and found the same translation, "control, adjust, regulate" for both.
But they are not identical. The major difference is:

調整 has the meaning of "negotiation", but 調節 doesn't.

Imagine that you are driving two of your friends to some airport.
If friend A requested you to speed up, while friend B wanted you to drive slowly, there is a conflict of opinion. "調整" is used in such a case.

友人Ａはスピードを上げることを望んだけれど、友人Bは安全運転でゆっくり行くことを求めた。
そこで私は２人の意見を調整して、時速80kmぐらいで走ることに決めた。

In this case, "調節" is not suitable. Only "調整" fits the context.

After the negotiation, you decided to drive at 80km/h.
Then you will control the accelerator pedal to go at 80km/h.
This operation is not a negotiation. So "調節" is natural for describing that.

「調整」は、「行き過ぎを抑える」という意味で使われることもあります。

Imagine that there are some movements, such as:

Urbanization of rural areas.
Flow of a river.

When these movements are progressing too rapidly, the administrator of that must take a measure to slow them down.

"調整" can be used in this situation. "調節" can't.

In such a situation, "調整" means "slow down".