essential oil; volatile oil
Commonly used in aromatherapy, cosmetics, and natural products. Refers to concentrated plant extracts.
ラベンダーの精油をアロマディフューザーに入れる。
I put lavender essential oil into the aroma diffuser.
refined oil
A broader term for any oil that has been purified or processed. Less common than the essential oil sense.
この工場では原油から精油を生産している。
This factory produces refined oil from crude oil.
oil refinery
Compound of 精 (refine, pure) and 油 (oil). The term is used both for essential oils (plant extracts) and refined oils (processed petroleum or other oils).