"single object or thing," c. 1600, from individual (adj.). Meaning "a single human being" (as opposed to a group, etc.) is from 1640s. Colloquial sense of "person" is attested from 1742. Latin individuum as a noun meant "an atom, indivisible particle," and in Middle English individuum was used in sense of "individual member of a species" (early 15c.).
1851, historians' name for the Germanic runic alphabet; so called from its first six letters (th being a single rune), on the model of alphabet.
1610s, "practice of marrying only once in a lifetime," from French monogamie, from Late Latin monogamia, from Greek monogamia "single marriage," from monogamos "marrying only once," from monos "single, alone" (from PIE root *men- (4) "small, isolated") + gamos "marriage" (see gamete). As "condition of being married to only one person at a time," by 1708.
"insanity in regard to a single subject or class of subjects; mental action perverted to a specific delusion or an impulse to do a particular thing," 1820, probably on model of earlier French monomanie (1819), from Modern Latin monomania, from Greek monos "single, alone" (from PIE root *men- (4) "small, isolated") + mania (see mania).
Men of one idea, like a hen with one chicken, and that a duckling. [Thoreau, "Walden"]
late 15c., duelle (from late 13c. in Latin form), "a single combat," also "a judicial single combat," from Medieval Latin duellum "combat between two persons," from Latin duellum "war," an Old Latin form of bellum (see bellicose). The Old Latin word was retained in poetic and archaic language and apparently given a special meaning in Medieval or Late Latin of "one-on-one combat" on fancied connection with duo "two."
Sometimes also in Italian form duello. The English word by 1610s had taken on the specialized sense of "premeditated and pre-arranged single combat involving deadly weapons in the presence of at least two witnesses." General sense of "any contest between two parties" is from 1590s.
"two or more letters intertwined," 1690s, from French monogramme or directly from Late Latin monogramma (5c.), from Late Greek monogrammon "a character formed of several letters in one design," especially in reference to the signature of the Byzantine emperors, noun use of neuter of monogrammos (adj.) "consisting of a single letter," literally "drawn with single lines," from Greek monos "single, alone" (from PIE root *men- (4) "small, isolated") + gramma "letter, line, that which is drawn or written" (see -gram). Earlier it meant "sketch or picture drawn in lines only, without shading or color," a sense also found in Latin and probably in Greek but now obsolete in English. Related: Monogrammatic.