Although lexicography and terminology are both disciplines that deal with words and their meanings, the approach to how words are related and organized with respect to their meanings is quite different:
In lexicography, words are typically alphabetically arranged with the different meanings or senses of each word listed with that word. This means that a single word form may have many different meanings associated with it. For example, the word volume will be listed as a single entry with all its meanings: (1) the amount of something; (2) the loudness of a sound from a radio, CD player, etc.; (3) a book or publication; (4) a unit of physical media which contains computer data (e.g. a disk or CD-ROM); etc.
In terminology, words are conceptually arranged with related terms (synonyms or near synonyms) attached to the same concept or meaning. This means that words that are spelled the same but mean different things (homographs) will be in separate entries, and an entry may also contain words that look nothing alike. In the example of volume, the four senses listed above would each be a separate entry. Conversely, the words clock speed, clock rate and hertz time could all be arranged in a single entry under the concept: “The rate at which the clock in an electronic device, such as a computer, oscillates.”