Definition -
(1) In its primordial philological sense, the word denoted "a language element that cannot be broken down further."
(2) For its modern linguistic senses, see inflectional root and lexical root.

Oxford English Dictionary -
The term's first citation in this sense is from 1530:
"His thre chefe rotes, that is to say, his theme, his preterit participle, and his present infynityve."
(Jehan Palsgrave, Lesclarcissement de la langue françoyse, Introd. 31)

Quotation -
"The shortest and best way of learning a language is to know the roots of it; that is those original primitive words, of which many other words are made."
(Source: 1740 Chesterfield Lett. lxiii. (1792) I. 177 )

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