名詞 nonessential:

1. anything that is not essential
   同義詞：inessential

形容詞 nonessential:

1. not of prime or central importance- Pubs.MLA
   同義詞：incidental

non.es.sen.tial

adj.（形容詞）
Having little or no importance; not essential.
非必要的，不重要的：有極少或根本沒有重要性的；非本質(zhì)的
Biochemistry Being a substance that is required for normal functioning but does not need to be included in the diet because of the body`s ability to synthesize it from other nutrients.
【生物化學(xué)】 （氨基酸）非必需的：是正常的運(yùn)轉(zhuǎn)所需要的物質(zhì)的，但因?yàn)闄C(jī)體有從其它營(yíng)養(yǎng)成分合成它的能力，因此不需要被包括在日常的食物中的