This research included the issue of foreign words according to Ibn jinni (d. 392 AH) in his book (Characteristics) It included an introduction and then astudy that dealt with foreign words mentioned in (Characteristics) in an organized manner According to the letters of the alphabet and what Ibn jinni said about Characteristics, then the sayings of the scholars about them, starting from the oldest to the newest, and explaining its origin through that and the changes that occurred in it, in addition to what Ibn jinni mentioned of a few foreign words that are not used in the Arabic language, and a distinction between the Arabic language and the Ajamiya language .