A prefix is a word part that has its own definition.  It can be attached to the front of a base or root word to create a new meaning for the base or root word.  Analyzing the two parts together create one new definition for a word. 

The word prefix itself is actually composed of two parts - a prefix and a Latin root word.

                                    pre + fix

             'pre' means before + 'fix' is from the Latin figere meaning to fix. 

Prefix, therefore, means a word that is 'fixed' or attached before the root/base word. 

Many categories define the intentions of prefixes.  See the chart below for a few examples.

Prefixes Expressing Amount or Extent

Prefix              Meaning                English Words

multi-                many, much            multicultural, multitude

ultra-                 beyond                    ultrasound, ultramodern

super-               more than                superlative, superfluous

Prefixes Expressing Negation

Prefix              Meaning                 English Words

counter-            opposite                  counterfeit, counteract

in-                    not                          indecisive, indecent

non-                 not                          nonsense, noncommital

Prefixes Expressing Location

Prefix              Meaning                 English Words

para-                beside                      parallel, parachute

per-                  throughout                pervade, persuade

with-                 back, away              withhold, withdraw

Prefixes Expressing Union 

Prefix              Meaning                 English Words

co-                    together                  coordinate, cooperative

col-                   with                        colleage, collect

sym-                 together                  symbol, symphony