To concatenate means to string together different things. Concatenating "snow" and "ball" produces "snowball." But what would the opposite action be? What is the name of the action used to derive two words from one?
(My dictionaries don't list any antonyms, and Googling revealed how to do the opposite but not what it's called.)
Edit: I had programming parlance in mind, so I've reflected that in the question title.
Looking strictly at the Latin roots of concatenate:
concatenare, from Latin com- + catenare, to chain [MW]
com- is the Latin prefix meaning "together, with."
dis- is the Latin prefix meaning "apart."
(de- means "down or away from," so you can make the case for that as well.)
So: discatenate, or decatenate.
Edit: As I (and FF) noted in a comment, decatenate is used in biology/biochemistry to describe the unlinking of a chain of chemical elements.
I would use split to mean the opposite of concatenate. I don't know if there's a better choice, but I've seen split used with this particular meaning in mind. Of course you should also specify how you will split the word, since you could split it at any point(s), and into more than 2 parts.
join and concatenate aren't exactly analogous in the programming world. To join is to concatenate the elements in a list, but each separated by some delimiter.
the action used to derive two words from one
decompose - to separate or resolve into constituent parts or elements; disintegrate
(in the same vein as "deconstruct", which has already been mentioned)
"Snowball" can be decomposed into its constituent parts: "snow" and "ball".
When getting the original words from a word formed by concatenating words, or possibly modified parts of words, the previously-mentioned divide and split spring naturally to mind. However, the verb cleave has to recommend it its sense "to split along a natural plane of division" (of a crystal), which can be seen as metaphor for dividing the composite word into natural parts. Another verb that suggests splitting at natural divisions is burst, in its sense "to separate formfeed at perforation lines".
I'm going to go with separate. I think it's one of the closest available to the desired meaning, and it has the bonus of rhyming with (and being at least vaguely close in length and syllables as) concatenate.
I don't think there's a truly great answer, mainly because concatenate isn't the best antonym for anything else. Many people mentioned split, which is a perfectly good word for the job, but the best antonym for split would probably be join.
The approach of using dis-, de-, or un- is certainly logical enough, but such a word feels constructed and unnatural without the benefit of widespread use. (Even if such words are in actual use, they are still far less frequently used than concatenate, especially in nontechnical contexts).
I think of concatenate as a programming word so I'll give you a programming antonym:
parse - 'to resolve (as a sentence) into component parts of speech and describe them grammatically'
As concatenate means to "link together" parse means to separate out.
Parse infers intelligence behind the action. Concatenate doesn't require any intelligence, just brute force, put this thing after that thing. Split has the same feeling for me where brute force rather than intelligence comes into mind (other than when slitting atoms lol). Same with separate for the antonym, doesn't require intelligence.
There are lots of words you could use: dichotomize, separate, and divide, to name a few. As mentioned by others, split also works.
Dichotomize is not very common, so you may want to avoid using it, for fear of sounding pretentious. Divide is nice because it can be used even if you are splitting the word into more than two parts.
Extract is another viable possibility.
separate from your list. I think it can go head-to-head against split any day :)
In general, I'm inclined to agree that split is a suitable term for retrieving the component words within, say, "snowball". It's certainly a standard term in a programming context, for the kind of trivial separation dumb code easily performs.
But with a slightly less "transparent" word, such as goshawk, I think it might be better to say you deconstruct it into "goose" and "hawk".
deconstruct - to expose or dismantle [a] structure.
I agree with most of what has been said about split/join. However, it's interesting to note that split has no way to know what the root words in your example are. That is, that the split should occur between snow and ball.
The more general case is referred to as tokenization. Split typically implies a character such as space, comma, CRLF, etc. to split on.
So, for example, a tokenizer would have enough information about the compositional root words of English to recognize that snow and ball are the tokens and break down the compound words accordingly.
It's interesting Frustrated would suggest 'split' because in the programming language Perl, the functions to respectively join two strings, and split two strings in half are respectively: Concatenate, and Split!
I'm pretty sure the guy who wrote Perl had the same dilemma, and that's the best he could come up with!
I guess you could make up a word, and say uncatenate, decatenate or something along those lines.
As a software developer I prefer split, unlink and disjoin but typically pick any that best describes the context and usage of what I'm creating. Not sure if that helps any.
Splitting the text would describe the action, and to do so would require a separator, or rules of separations. Stemming would define the linguistic concept.
I'd use stem if your original meaning of concatenate tended towards compound.
If you were of a software bent, I would say substring. While I don't think it is legitimately a verb, I have heard it often used as one when describing the act of breaking down a string of characters into any number of smaller strings, whether they be individual characters, or several.
Keep in mind that substring-ing does not assume that the resulting strings will be intelligible.
In programming specifically, there isn't an opposite of "concatenate". The concept makes no sense.
"Split" is probably the least silly alternative. But I wouldn't call it the opposite of concatenation in a programming context. In general usage, perhaps.
Nearly every programming language has an operator for string concatenation: ++ in Haskell, + in Python, . in PHP, etc. No language has an operator for the opposite of concatenation.
If you tell me "I concatenate 'shadows' and 'linger'", then I know exactly what the result is. If you tell me "I split 'shadowslinger'", then I have no idea what the result is; the operation is not well defined. I might guess that it would be "shadows" and "linger". But it could easily be "shadow" and "slinger". Or it might only be coincidence that it looks like English, and the split could have nothing to do with that.
The opposite word to concatenate is dissociate. Concatenation means joining two words and dis-concatenate or dissociate (dis-associate) is the synonymy.
Here's a list from Thesaurus.com, down at the bottom of the page:
Main Entry: consolidate
Part of Speech: verb
Definition: combine; make firm
Synonyms: add to, amalgamate, amass, band, bind, blend, build up, bunch up, cement, centralize, compact, compound, concatenate , concentrate, condense, conjoin, connect, densen, develop, federate, fortify, fuse, harden, hitch, hitch on, hook up with, incorporate, join, league, mass, meld, mix, plug into, pool, reinforce, render solid, secure, set, slap on, solidify, stabilize, strengthen, tack on, tag on, team up with, thicken, throw in together, tie in, tie up with, unify
Antonyms: disjoin, disperse, divide, part, separate
Given the difference in meaning between "consolidate" and "concatenate", I'd limit the antonyms in that list to "divide", "part", and "separate".
In most programming languages with C-based syntax, concatenate usually means to link strings or characters together. The fact that the strings usually happen to be words is somewhat irrelevant, because the computer (and hence the programmer) is handling them as a sequence of characters; like linking track from a toy train set together. The answer depends on what you're trying to do. One possibility is 'parse' as others suggest, because it means to separate out an aggregated entity, like a string of characters. However, parsing also implies computationally manipulating each piece or segment as it's separated from the whole. Another is 'split,' because that also applies to strings.
If the originator of the question is translating or editing a programming text, it would be best to verify your choice with the programming language of concern. Every programming language has its own parlance, largely influenced by the standard functions available in each language's respective code libraries or API's (application programming interface). For an example of what I'm talking about, here's java's api: http://docs.oracle.com/javase/6/docs/api/java/lang/String.html
A word of caution: programming jargon is dictated largely by the programming language being used, and by extension, it's syntax. Webster's thesaurus or the classical roots of a word probably aren't your best resources for answering this question.
Depending on what you mean by it, antonyms of catenate or the needlessly wordier concatenate might be detach or perhaps separate — but I’m rather unfond of unjoin. ☹
However, if you actually mean to chomp letters off the end and discard them, you probably want the mysteriously underused apocopate, which abbreviates or shortens a word, usually by a letter or a syllable. It comes to English right out of Latin, and in turn right out of Greek ἀποκοπή.
Truncate — Shorten (something) by cutting off the top or the end: "a truncated cone shape".
