Prescriptive Rules of Grammar: govern the version of English considered appropriate for use by educated speakers (the version designated as Standard American English)
Descriptive Rules of Grammar: describe how our grammatical system operates, rules that are the same for all speakers of English
Watch the former U.S. president Barack Obama's oath of office and think about the three questions below.
What did Obama change in the corrected sentence?
“I, Barack Obama, do solemnly swear that I will faithfully execute the office of president to the United States.” (original version)
“I, Barack Obama, do solemnly swear that I will execute the office of president to the United States faithfully. ” (corrected version)
2. What prescriptive rule was violated in the original version?
3. In informal speech, is it acceptable to put adverbs in front of verbs that they modify? (e.g., We'll quickly go over the reading and then move to the exercises.)
Answer key:
The change is with the position of the adverb 'faithfully' which modifies the verb 'execute'.
The prescriptive grammar rule is that manner adverbs (e.g., faithfully, solemnly) should go after the verb (e.g., execute, swear) that they modify.
In informal speech, it's perfectly fine to place adverbs before the verbs they modify.
*If the object of a verb is too long (for 'execute') or for the purpose of emphasis (for 'swear'), adverbs can be moved in front of the verbs that they modify.
Shall I stick to prescriptive grammar rules all the time?
It depends on the communicative context. In academic and professional writing, one should try their best to obey prescriptive grammar rules. However, in informal contexts, there's more flexibility.
In fact, professional writers are known for departing from prescriptive grammar rules. For example:
“Fly to others that we know not of.” (Shakespeare ended sentences with prepositions)
“When Mr. Collins said any thing of which his wife might reasonably be ashamed (of), which certainly was not unseldom, she involuntarily turned her eye on Charlotte.” (Jane Austen used double negatives)
“But before the captain could answer, a major appeared from behind the guns. (William Faulkner started sentences with conjunctions)
The rule of thumb is that one should know which rules they are breaking before actually breaking the rules.