hy-

• hu-

From Middle Welsh hy-, from Old Welsh hi-, from Proto-Brythonic *hu-, from Proto-Celtic *su-, from Proto-Indo-European *h₁su- (“good”). Cognate with Cornish he- and Ancient Greek εὐ- (eu-, “good”).

• IPA^(key): /hə/

hy-

1. affirmative prefix, emphasises prefixed word

   ‎hy- + ‎rhwydd (“easy”) → ‎hyrwydd (“very easy”)

   ‎hy- + ‎glân (“clean”) → ‎hylan (“hygienic”)

2. added to verbal roots, indicates 'easy to X', 'X-able'

   ‎hy- + ‎plyg (“folded”) → ‎hyblyg (“flexible”)

   ‎hy- + ‎byw (“alive”) → ‎hyfyw (“viable”)

• R. J. Thomas, G. A. Bevan, P. J. Donovan, A. Hawke et al., editors (1950–present), “hy-”, in Geiriadur Prifysgol Cymru Online (in Welsh), University of Wales Centre for Advanced Welsh & Celtic Studies