a prefix occurring in loanwords from Greek (diabetes; dialect) and used, in the formation of compound words, to mean “passing through” (diathermy), “thoroughly,” “completely” (diagnosis), “going apart” (dialysis), and “opposed in moment” (diamagnetism).
The Day After Halloween Is Actually Called HallowmasHalloween is actually just the beginning of a string of otherworldly holidays. The tricks, treats, and customs of Halloween, now mostly secular, are based in part on an ancient Christian festival that spans November 1st and 2nd.
Also especially before a vowel, di-.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for dia-
through, throughout, or duringdiachronic
(in botany) at right anglesdiatropism
in opposite or different directionsdiamagnetism
Word Origin for dia-
from Greek dia through, between, across, by
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Medicine definitions for dia-
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Science definitions for dia-
A prefix meaning through or across, as in diameter, the length of a line going through a circle.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.