英汉双语：精油(Essential oil)是什么？

What is an Essential Oil ?

Essential oils are the volatile, aromatic oils obtained by steam or hydrodistillation of botanicals. Most essential oils are primarily composed of terpenes and their oxygenated derivatives.
Different parts of the plants can be used to obtain essential oils, including the flowers, leaves, seeds, roots, stems, bark, wood, etc. Certain cold-pressed oils, such as the oils from various citrus peels, are also considered to be essential oils but these are not to be confused with cold-pressed fixed or carrier oils such as olive, grapeseed, apricot kernel, etc. which are non- volatile oils composed mainly of fatty acid triglycerides.
Other aromatic, plant-derived oils, which technically aren't essential oils because they are solvent extracted, include Absolutes
(hexane followed by ethanol extraction), CO2's (liquid carbon dioxide used as the solvent) and Phytols or Florosols
(fluoro-hydrocarbon solvent).

甚麼叫精油呢? 精油是一種由植物中蒸餾或粹取出來的揮發性有香味的油.
大部份精油的基本成份都是來自於他們的氧化物和terpenes(不知道怎麼翻).
植物的不同部份會穫得不同的精油, 包括花, 葉, 種子, 根, 樹枝, 樹皮, 樹幹等.
像柑橘類的果皮, 都會用冷壓(冷搾)法取得精油, 但這和冷壓法取得的基底油
例如: 橄欖油, 葡萄子, 杏核仁等油, 是不一樣的. 這些基底油是非揮發性的,
主要都是由豐富的acid triglycerides組成. (這個我翻不出來)
其他有香味的植物油, 技術上來說不算是精油, 因為他們是溶劑粹取出來的.
包括脂吸法, 二氧化碳粹取法, 或是Phytols或florosols.

我自己加的:
可是一般花類的精油因為粹取困難, 所以會採用脂吸法去取得精油, 像是大馬士革 玫瑰或是茉莉等花朵類精油. 我們仍然會叫這些為精油, 但會用absolute來區分是採取甚麼方式取得的精油.