Here is a list of the most common prefixes and their meanings. You should find them easy to learn because they are almost all closely related to prepositions. Some prefixes don't have an easily translatable word or phrase. They have a general idea, or flavor, that they add to the meaning of the base. For example, the verb caedīmeans “to cut,” and the prefix ob has an “opposing,” “up close and personal” flavor. Put them together and you get occī dī, –ere, occī dī,occī sum (“to kill”).
|ā , ab||away, from||abeō(to go away)|
|ad||to, toward, near||adsum (to be present)|
|ante–||before, in front||antecedō (to go ahead)|
|con–||with, together, intense||conveniō (to gather)|
|dē–||down, from, bad||dē rideō(to mock)|
|dis–||scattered, apart, bad||discumbō(to sprawl)|
|ē –/ex–||out||exeō (to leave)|
|in||in, on, against||ineō(to enter)|
|ob–||opposing, counter, blocking||obvius (evident) (ob + via,“blocking the road”)|
|per–||thorough, intense||perterritus (thoroughly frightened)|
|prae–||ahead||praesum (to be in charge)|
|praeter–||except, beyond||praetereō(to pass by)|
|prō–||forward, in front||prō cē dō(to go ahead)|
|re–, red–||again, back||redeō(to return)|
|sub–||under, subtle||subrideō(to grin)|
|super–||over, above||supersum (to be left over, survive)|
|trans–, trā–||across||trā dō (to hand over)|
Some prefixes change their spelling slightly when attached to a word. The main reason this occurs is to make the word easier to say. These changes can make prefixes difficult to recognize.
A good example of these phenomena is the verb accipiī (“to welcome”; literally, “to take to one's self”). It is made of the prefix ad– (“to, toward”) and the verb capiī(“to take”). The d on ad changes to c to make it easier to say. This process is called assimilation.
Be aware of vowel weakening. Sometimes the vowel in a verb base changes a little when a prefix is attached. This is most common when a verb has an a or ae in its base. For example, add the prefix per– to faciō , facere, fē cī , factum and you get perficiō,perficere, perfē cī , perfectum.