the letters added to the beginning of a root that change its meaning. The most common prefixes are:

• ante- meaning before, e.g. antediluvian
• pre- meaning before, e.g. pre-war
• demo- meaning of the people, e.g. democracy
• il- meaning not, e.g. illegal
• multi- meaning many, e.g. multi-dimensional
• tri- meaning three, e.g. tricycle
• bi- meaning two, e.g. bicycle
• non- meaning not, e.g. non-event
• ir- meaning not, e.g. irregular
• semi- meaning half, e.g. semi-circle
• in- meaning not, e.g. incapable
• mis- meaning wrong, e.g. misplaced