word-forming element used in chemistry to coin names for simple compounds of one element with another element or radical; originally abstracted from oxide, which was the first so classified, in which the -ide is from acide "acid."
The suffix is really -dus (-do-), the -i- repr. the orig. or supplied stem-vowel ; it occurs without the vowel in absurdus, absurd, blandus, bland, crudus, raw (crude), etc. [Century Dictionary]
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Harper, D. (n.d.). Etymology of lipid. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/lipid