The science of the origin and development of words. Most medical words are derived from Latin and Greek, but many of those from Greek have come through Latin and have been modified by it. Generally, when two Greek words are used to form one word, they are connected by the letter “o”. Many medical words have from one or more roots — forms used or adapted from Latin or Greek — and many are modified by a prefix, a suffix, or both. A knowledge of important Latin and Greek roots and prefixes will reveal the meanings of many other words.