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 ).
PRE-
Meaning of PRE- in English
Longman Pronunciation English Dictionary. Английский словарь произношений Longman. 2012