Meaning of PRE- in English

PRE-

pre- BrE AmE ¦priː, pri, prə, ¦pre —Compare re- . As a productive prefix meaning 'before' (sometimes spelt with a hyphen), ¦priː (preadapt ˌpri ː ‿ə ˈdæpt , pre-sleep ˌpriː ˈsliːp◂ ). Otherwise, with a vaguer meaning, pri, prə before a consonant sound (prepare pri ˈpeə prə- AmE \ -ˈpe ə r ) ; but if stressed through the operation of a stressing rule usually ¦pre+ (preparation ˌprep ə ˈreɪʃ ə n ).

Longman Pronunciation English Dictionary.      Английский словарь произношений Longman.