doubly

Doubly is an adverb formed from the adjective double with the suffix -ly. It is used to indicate twofoldness or that something is done in two ways, to twice the degree, or in two directions. In everyday language, it often accompanies adjectives or participles: “doubly important,” “doubly reinforced,” or “doubly insured.”

In compound terms, it can describe duality in structure, such as a doubly linked list, where each element contains links to both the previous and the next elements. The word can also appear in technical phrases that emphasize dual characteristics or two simultaneous conditions.

Etymology: Doubly comes from Middle English double + -ly, from Old French doble, ultimately from Latin duplex meaning twofold or doubled. The evolution reflects the general development of the English word double into an adverb by the added suffix.

Usage notes: “Doubly” is distinct from “twice.” Twice refers to a frequency (two times), while doubly expresses a degree, quality, or duality. It is common in formal writing and in technical jargon. In mathematics and related fields, “doubly” appears in terms such as doubly stochastic matrices and doubly linked lists, where the sense of twofold structure or duality is central.

In summary, doubly signals a twofold or dual nature, whether describing degree, method, or structural properties, and remains a versatile term across everyday language and specialized disciplines.