What is ‘-ad?

‘-ad definition and meaning on Dictionary terms:

a suffix occurring in loanwords from Greek denoting a group or unit comprising a certain number, sometimes of years: dyad; triad.
a suffix meaning a??derived from,a?? a??related to,a?? a??concerned with,a?? a??associated witha?? (oread), introduced in loanwords from Greek (Olympiad; oread), used sporadically in imitation of Greek models, as Dunciad, after Iliad.


reference: https://www.dictionary.com/browse/-ad