ǵneh₃-
“to know, to recognise”Widely acceptedcognitionperception
Know, recognise, be acquainted with
This root underlies an enormous vocabulary of knowledge across IE: Latin gnōscere (know, recognise), Greek gignṓskō, English know and can, Sanskrit jñā-, and the -gnosis family (diagnosis, prognosis, agnostic).
Phonological Notes
AblautFull grade *ǵneh₃-, zero grade *ǵn̥h₃-.
LaryngealsContains h₃ (o-colouring).
Discussion
The root *ǵneh₃- generates one of the most extensive lexical families in Indo-European, encompassing verbs of knowing, nouns of knowledge, and adjectives of cognitive capacity. The semantic range extends from direct acquaintance ("to recognise") to abstract knowledge ("to understand").
Latin (g)nōscere ("to get to know, to recognise") and its more common compound cognōscere ("to learn, to investigate") yield an extraordinary number of English derivatives: cognition, recognise, cognisant, incognito, noble (from gnōbilis, "knowable, notable"), note, notion, notorious, and the legal term cognisance. The prefix i(g)n- in ignorant and ignore represents the negative *n̥- + *ǵneh₃-.
Greek gignṓskō (γιγνώσκω, "I know, I perceive") shows the characteristic Greek reduplication of the present stem. The nominal derivative gnṓsis (γνῶσις, "knowledge") gives diagnosis ("knowing through"), prognosis ("knowing beforehand"), Gnostic (from Gnostikós, "one who knows"), and agnostic (coined by T. H. Huxley in 1869 from a- + gnōstós). The gnṓmē ("judgment, opinion") underlies gnomon and physiognomy.
Sanskrit jñā- (jānā́ti, "knows") shows the satem shift *ǵ > j. The derivative jñāna ("knowledge") is a central concept in Hindu and Buddhist philosophy, and prajñā ("wisdom, insight") occupies a comparable position in Buddhist thought.
In Germanic, the root produces two distinct lines: (1) *knēaną > Old English cnāwan (Modern English know, with the silent k preserving the old initial cluster), and (2) *kunnaną ("to be able") > Old English cunnan (Modern English can). The bifurcation of knowing and being able reflects an ancient semantic distinction between cognitive knowledge and practical capacity.
The distinction between *ǵneh₃- ("to know by acquaintance, to recognise") and *weyd- ("to know by seeing, to have seen") is a fundamental feature of the PIE lexicon. Many daughter languages preserve reflexes of both roots, sometimes with specialised meanings: English know (from *ǵneh₃-) versus wit (from *weyd-), German kennen ("to be acquainted with") versus wissen ("to know a fact").