softener; softening agent
General term for a substance that softens materials, such as fabric softener, water softener, or plasticizer.
洗濯のときに軟化剤を入れると、タオルがふわふわになる。
If you add softener when doing laundry, towels become fluffy.
This softening agent has the effect of softening hard water.
Compound of 軟化 (softening) + 剤 (agent, chemical).