It is hard to get through a day without reading, writing, hearing or saying a word that does not begin with the re- prefix. That is possibly because much of what we do during the day can be described quite well using some word beginning with re. For example, in the morning, we go to work or school and then return home in the evening. We repair, restore and replace things that are broken around our houses. We restate and reiterate our opinions, recite the reasons for our decisions and remind ourselves of the things we need to do. We review and revise reports and resolve issues. Sometimes we resent or regret what happens to us while other times we are relieved and rejoice. We reply to email and we repay our debts. And when it gets very late, we retire to our bedrooms. And one can simply add the re- prefix to practically any action verb in English and come up with another, legitimate action verb that is used almost if not as often as the verb it was formed from.
Our everyday familiarity with the re- prefix convinces us that we understand exactly what it means. Ask any high school student and they will probably tell you that the re- prefix means "again". And if you look up the prefix in any dictionary, you will find that it, in most cases, means "again". One would pretty much have to be a complete nincompoop then to argue that the prefix re- does not mean "again". Who in their right mind, given what one would be up against, would argue with what both the experts and our own common sense tell us is true?
And yet, that is exactly what I am going to tell you. You are going to have to reconsider what you thought you knew about the re- prefix, because everything you think that you know and what the experts have been saying about it is essentially wrong. The re- prefix does not actually mean "again". And to prove that, we need to take an honest look at a few of the many words that begin with re- prefix, beginning with the word regulation, where the prefix re- clearly does not mean "again".
The word regulation is related to the word regular. Things that are uniform (i.e., regular) are often uniform because of regulations. To regulate is not to gulate again. One generally makes things regular (i.e., standardized, normalized) by removing irregularities or inconsistency with regard to action and form. Here the Olin translation for the word remove accurately represents the idea of such removal: "irregularity out of; irregularity related later (uniform) movement out of". Note that remove does not mean "move again".1 In common usage, the word remove roughly means "move something away" or "get rid of". And the primary reason for removing something is because it does not fit or conform.
Clearly, in countless words the re- prefix does appear to mean "do again" (e.g., restate, repopulate, reiterate, recalculate, reformulate, review, etc). However one must understand the most common reason why one does something over again: because of inconsistencies that resulted the prior time one did something or that arose subsequently. For example, when we review something, we are not simply viewing something again; we are viewing it again with a purpose: to find errors.
Another word that begins with the re- prefix where the meaning of re- is clearly not "again" is result. The word result is not a simple concatenation of re- and sult. The word result, which can also be used as a noun, does not translate as "sult again". And while other words appear to share the same sult "root" (e.g., insult, consult), they are not cloesly linked conceptually. In fact, according to the Online Etymology Dictionary, the sult of consult comes from a Latin verb meaning "to gather the Senate" while the sult of insult and result derives from salire, a Latin word meaning "to take a leap" (which appears to be what the etymologists have done!). But again the Olin translation for the word result makes it pretty clear exactly what the word was intended to describe: "irregular/unpredictable movement out of, related changes (to) original surface (of) that", where the "original surface" or level represents the original, undisturbed state of things.
The word resume also has tucked away within it the idea of an irregularity. There is, after all, no English word sume. When we resume what we were doing, we are not sume-ing again. And if one looks up the Latin definition of sume or sumere, one finds a litany of meanings like "fascinate", "borrow", and "inflict punishment" (which leaves this author asking the question "Say what?"). In fact it almost appears that the authors of the dictionary entry had no clue as to what the alleged word actually meant so they decided to give it every meaning that it possibly could have. Surely, if a word was really that useful in Latin it would have made it into English with similar utility. However, even the Italians appear to have suffered complete amnesia as the only meaning the word sumere has in Italian is as a reference to a priest taking communion during the Eucharist. And yet, the English language has a number of words with the alleged sume root: resume, consume, presume, and assume. Unfortunately, while presume and assume appear to be conceptually related, they bare little similarity conceptually with respect to the other words, resume and consume.
But all the confusion goes away completely if one translates ume correctly. Ume translates as "original movement related out of". It is a crystal clear reference to prior movement. When one resumes what one was doing one is doing the same thing one had been doing before one had stopped what one was doing. And when one assumes or presumes, one is expecting that which was true before (i.e., that which had been happening) will be true later (i.e., will continue to happen).
As for consume, the relationship is a little more complicated. When one consumes, one is using up that which one had stored away previously. Note that the con- prefix, as in discontinuity, refers to a "flowing out of containment". Thus consume refers to a an outflow that was related to (i.e., the reverse of) a previous movement into containment (i.e., an inflow).
Resuming our analysis of the word resume, we note that it refers to doing the same thing that one was doing before one stopped doing what one was doing. Here one needs to ask again why someone would stop doing what they were doing (such as weaving) for a brief moment. The answer: one stops if one notices an irregularity, either an irregularity in the results of ones actions or an irregularity that might interfere with what one was doing (such as finding a large rock in a field while plowing). And that is exactly what the re- in resume means. It does not mean "again" as the dictionary and a layman's familiarity with the word would have you believe. It means "because of an irregularity".
Another word to look at is retreat. Again, there is no military term treat. An army does not "treat" and then "treat" again. If you believe that retreat decomposes as re- treat, then I have some land in Florida that I would like to sell you. I am not saying that the apparent treat "root" does not have a valid meaning, but it only has meaning as part of the word retreat, even though the re- "prefix" retains its meaning "irregularity out of". The word retreat translates as "irregularity out of; that movement out of prior surfaces related". Translated into human-speak, the word retreat is saying "because unexpected stuff happened, we have to leave the fields of battle". (Quite frankly, it doesn't get much clearer than that!)