prefix /ˈpɹiːfɪks/noun 5verb 2forms 5 noun5 •Something placed before another •A morpheme added to the beginning of a word to modify its meaning, for example as, pre- in prefix, con- in conjure, re- in reheat, etc. •A set of digits placed before a telephone number, to indicate where the number is based, what type of phone number it is (landline, mobile, toll-free, premium rate etc.)in the UK, a number with an 0800 prefix is a toll-free number. •A title added to a person's name, such as Mr. or Dr. •An initial segment of a string of characters.The string "abra" is both a prefix and a suffix of the string "abracadabra". verb2 •To put or fix before, or at the beginning of something; to place at the start.His requests for money were usually prefixed by an apology.You must prefix the number with the area code. •To determine beforehand; to set in advance.They duly arrived at the prefixed hour. formsprefixed · prefixt · prefixing · prefixes · prefices