pre- Also prae-.
Prior to; before; earlier; in front of.
[Latin prae, before.]
Many words containing this form were created in Latin: premature (Latin praematurus, very early, from maturus, ripe), preside (Latin praesidere, from sedere, sit), precaution (Latin praecavere, from cavere, take heed, beware of), precinct (Latin praecinctum, from cingere), preclude (Latin praecludere, from claudere, to shut), preposition (Latin ponere, to place), prescribe (Latin praescribere, direct in writing, from scribere, write).
The form is widely used to form new terms by attaching it to English stems: prepay, preflight, prefrontal. It is frequently hyphenated when the stem begins with a vowel, as in pre-adolescent, pre-arranged, pre-existing, pre-ignition. British English often hyphenates words which in American usage commonly appear without one: pre-war, pre-school, pre-book, pre-cooked, pre-planned.
The spelling prae- is now used only for words which are regarded as Latin or which relate to Roman antiquity: praetorian, of each of two ancient Roman magistrates ranking below consul; praenomen (Latin nomen, name), an ancient Roman's first or personal name.