dia

through, across

Spelled dia · dia 'through, across, apart'

Greek dia carries things across: a diagonal crosses between corners, diaphanous cloth lets light through, and a diagram marks relationships out.

Words built from it

diatribe — a long, bitter verbal attack
dia- (thoroughly) + tribe (rub)
diaphanous — light and thin enough to see through
dia- (through) + phan (show) + -ous (having the quality of)
diametric — at opposite extremes; completely opposed
dia- (across) + metr (measure) + -ic (relating to)
diagonal — extending slantwise between corners
dia- (across) + gon (angle) + -al (relating to)
diagnosis — identification of an illness or problem from its signs
dia- (apart) + gnos (know) + -sis (process)
diagram — a drawing that explains structure or relationships
dia- (across) + gram (something written or drawn)
dialogue — a conversation or exchange of ideas
dia- (through) + logue (speech)

diarist — Comes from diary plus -ist. Diary traces to Latin diarium (daily record) and dies (day), not Greek dia.