Choi, Byung Jung. 2002. Productive Word-Formation Patterns in Old English. The History of English, 14. In this article we are going to find out the principles of productivity in Word-Formation patterns in Old English. Words are used to convey the implicit concept of syntax, which describes the patterns or rules according to which words are combined into larger linguistic structures. That is, words make up the vocabulary (i.e.,lexicon) of a language which is used in a variety of senses in everyday language. According to Scheler (1961) there were about 23,000-24,000 words in Old English while there are about 2,000,000 words in modern English. Consequently, we wonder how they managed to express themselves in everyday life with a small number of words. It is the aim of this thesis to find out which other methods were used to express ideas. Important works, such as Beowulf, Cynewulf, The Blickling Homilies, and The Anglo-Saxon Chronicle were used to get data. The basic principles of the productive patterns were studied as the following items; (1) word-formation by vowel shift (2) word- formation by stem+inflection (3) word-formation by compounding (4) word- formation by association. These basic principles will be explained using a variety of examples. Foreign loan words occupy more than 70% of English language while there were only 3% in Old English. Old English is descended from Germanic word-families, so most of its rules and senses are related to it. Through this study it appears that Old English word-formation is productive.