Etymology
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id (n.)
1924, in Joan Riviere's translation of Freud's "Das Ich und das Es" (1923), from Latin id "it" (as a translation of German es "it" in Freud's title), used in psychoanalytical theory to denote the unconscious instinctual force. Latin id is from PIE pronominal stem *i- (see yon).
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plasmid (n.)

"genetic structure in a cell that can replicate independently of the chromosomes," 1952, from plasma + -id.

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-id 
adjectival word-forming element, especially in zoology, "belonging to, connected with, member of a group or class," in some cases probably via from French -ide, back-formed from Modern Latin names of zoological classes in -idae, as arachnid "a spider" from the biological class name arachnidae.

This -idae is the plural of Latin -ides, a masculine patronymic (indicating "descent from"), from Greek -ides "son of," denoting descent from the person to whose name it is attached (such as Heraklides).

In astronomy, of meteor showers, "having its radiant in" the constellation named (Perseid, Leonid, etc.), it probably represents Latin -idis, from Greek -idos, the genitive of the feminine form of the patronymic suffix.
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-idae 
word-forming element used to coin family names in zoology (by being suffixed to the name of the genus whence that of the family is derived), from Latin -idae, plural of noun suffix -ides (see -id).
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chrysalid (adj.)

"pertaining to a chrysalis," 1801, see chrysalis + -id. As a noun variant of chrysalis, 1620s, perhaps from French chrysalide.

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plastid (n.)

"unicellular organism, individual mass of protoplasm," 1876, from German plastid, coined by Haeckel from Greek plastos "formed, molded" (verbal adjective from plassein "to mold;" see plasma) + -id.

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Cepheid (n.)

type of variable star, 1904, from Delta Cephi, the name of the first such star identified, which is in the constellation Cepheus. With -id.

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hominid (n.)
"one of the family of mammals represented by man," 1889, from Modern Latin Hominidæ the biological family name (1825), from Latin homo (genitive hominis) "man" (see homunculus) + -id. As an adjective from 1915. Related: Hominine (adj.).
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id est 
Latin, literally "that is (to say)," from id "that," neuter of is, from PIE pronominal stem *i- (see yon). For est, see is. Usually abbreviated i.e. "to write, or even to say, this in the full instead of in the abbreviated form is now so unusual as to convict one of affectation" [Fowler]. It introduces another way to say something already said, not an example of it (which is e.g.).
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*kae-id- 

*kaə-id-, Proto-Indo-European root meaning "to strike."

It forms all or part of: abscise; avicide; biocide; caesarian; caesura; cement; chisel; -cide; circumcise; circumcision; concise; decide; decision; deicide; excise (v.); excision; felicide; feticide; filicide; floricide; fratricide; fungicide; gallinicide; genocide; germicide; herbicide; homicide; incise; incision; incisor; infanticide; insecticide; legicide; liberticide; libricide; matricide; parricide; patricide; pesticide; precise; precision; prolicide; scissors; senicide; spermicide; suicide; uxoricide; verbicide.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit skhidati "beats, tears;" Latin caedere "to strike down, fell, slay;" Lithuanian kaišti "shave;" Armenian xait'em "to stab;" Albanian qeth "to shave;" Middle Dutch heien "to drive piles," Old High German heia "wooden hammer," German heien "beat."

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