You do get a few hits for this phrase if you Google it, but I recognize that it probably needs to be defined.
Syntax refers to a language’s rules about how words fit together in a sentence. Many of these rules go unstated most of the time.
If I were to rephrase the previous sentence as follows, you would know that I wasn’t following the rules of English syntax:
Go unstated most of the time many of the rules.
Few native speakers of English would say such a thing. (Yoda’s native tongue was not English.) But native speakers do sometimes write sentences whose syntax suffers from indeterminacy: it starts out heading in one direction but then takes an unexpected — and ungrammatical — turn, leaving readers scratching their heads and forcing them to start over.
When I encounter such a sentence, I find myself mentally repunctuating it as I read it for the second or third time. Read this sentence carefully:
Abraham Lincoln was in his forties as a national crisis erupted over slavery, going back into politics for this reason, Lincoln ran for the senate and the presidency.
Did you notice any problems? This sentence is a form of run-on known as a comma splice. Furthermore, it suffers from syntactical indeterminacy. If you were indeed reading every word, you probably assumed that the phrase “going back” was going to refer to the crisis over slavery. Instead, the (imaginary) writer started over with a new independent clause that had no syntactical connection to the previous independent clause. The comma should have been either a period or a semicolon (which indicates a full stop in most situations).
If you were skimming over the words (barely reading), you might not even notice such an error, but if you were reading carefully, you probably had to stop in your tracks, go back, and reread. As far as I can tell, the human brain can only track one syntax at a time, so it doesn’t do so well when the syntax suddenly shifts. Creative writers, of course, sometimes play syntactical tricks on their readers, but if you are writing to argue or describe or explain, you probably don’t want to throw up roadblocks to reader comprehension.
To avoid syntactical indeterminacy when you are integrating quotations into your own sentences, and thus into your own syntax, you need to make sure that the syntax of your sentence matches up with that of the quotation. Just because you are quoting does not mean that the rules of syntax no longer apply!
Usually, if you are quoting part of a sentence, you can find a way to work it naturally into your own sentence, with no special punctuation. For instance:
The 1848 Seneca Falls “Declaration of Sentiments” echoed the Declaration of Independence, stating that “all men and women are created equal.”
If you are quoting more than one independent clause, however, you need to set the quotation off with a colon, thus separating the syntax of your sentence from that of the quotation. If you don’t use a colon in such a situation, you create a run-on. In other words, if a quotation starts inside your own syntax, it must end there, too. Here’s an example of an error:
In his second inaugural address, Abraham Lincoln noted the surprising length and severity of the Civil War, “Neither party expected for the war, the magnitude, or the duration, which it has already attained. Neither anticipated that the cause of the conflict might cease with, or even before, the conflict itself should cease.”
Above, Lincoln’s sentences are simply spliced onto the previous sentence, creating a comma splice. Notice how the next example runs on:
Much like the Declaration of Independence, the 1848 Seneca Falls “Declaration” included a long list of grievances, such as “He has never permitted her to exercise her inalienable right to the elective franchise. He has compelled her to submit to laws, in the formation of which she had no voice. He has withheld from her rights which are given to the most ignorant and degraded men–both natives and foreigners.”
This kind of error, unfortunately, does appear in copyedited, published writing. The problem here is that, technically speaking, the three independent clauses of the quotation have been inserted into the syntax of the original sentence, which creates a series of run-on sentences. Again, just because you are quoting does not mean that the rules of syntax no longer apply. All that this passage needs is a colon to set off the quotation. The rule-abiding reader will know that the colon constitutes a syntactical break.