FANBOYS is a mnemonic for the seven coordinating conjunctions in English: For, And, Nor, But, Or, Yet, So. These seven words have the specific grammatical function of connecting elements of equal grammatical rank — words to words, phrases to phrases, independent clauses to independent clauses. Knowing how they work prevents some of the most common punctuation errors in academic writing.

What coordinating conjunctions do

A coordinating conjunction joins two or more elements that have the same grammatical function. The elements it joins are coordinate — they operate at the same level of the sentence.

This means FANBOYS can connect:

Two nouns: cats and dogs

Two adjectives: careful but thorough

Two verb phrases: reviewed the data and submitted the report

Two independent clauses: The results were unexpected, but the methodology was sound.

The last use — joining two independent clauses — is the one that generates the most punctuation questions.

Punctuation with FANBOYS

When a coordinating conjunction joins two independent clauses, a comma precedes the conjunction:

The first experiment failed, so the team redesigned the protocol.

The sample size was small, yet the findings were consistent with earlier research.

When FANBOYS joins elements that are not independent clauses (noun + noun, verb phrase + verb phrase), no comma is needed:

     She reviewed the data and submitted the report. (two verb phrases sharing a subject — no comma)

                 The analysis was thorough and convincing. (two adjectives — no comma)

The comma splice error — joining two independent clauses with a comma but no conjunction — is one of the most common errors in academic writing. The fix is either to add a coordinating conjunction after the comma, replace the comma with a semicolon, or split into two sentences.

The results were unexpected, the team reviewed the methodology. → comma splice

The results were unexpected, so the team reviewed the methodology. ✓

The results were unexpected; the team reviewed the methodology. ✓

The meaning of each conjunction

Each FANBOYS conjunction carries specific meaning:

For introduces a reason (similar to because, but more formal and somewhat archaic in contemporary usage): The experiment was stopped, for the conditions had become unsafe.

And adds information: The first group showed improvement, and the second group remained stable.

Nor negates and adds: The results were not significant, nor were they in the expected direction.

(Note: nor typically requires inversion of the subject and auxiliary in the clause that follows.) But shows contrast: The study was well-designed, but the sample was not representative.

Or presents alternatives: Participants could withdraw from the study, or they could choose to continue with modified conditions.

Yet shows contrast with a sense of surprise (similar to but, slightly more emphatic): The intervention was minimal, yet the effect size was substantial.

So introduces a consequence or result: The data were incomplete, so the analysis was limited to the available cases.

Starting sentences with FANBOYS

The old rule against beginning a sentence with a coordinating conjunction has no grammatical basis and has never been endorsed by major usage authorities. Starting a sentence with And, But, or So is stylistically common and often effective for emphasis. The question is whether the effect is warranted in the register you’re writing in: it’s more common in journalism and general nonfiction than in the most formal academic prose.

Trinka’s grammar checker identifies comma splice errors and incorrect punctuation around coordinating conjunctions in academic and professional writing.

References

Huddleston, R. & Pullum, G. K. (2002). The Cambridge Grammar of the English Language.

Cambridge University Press.

Garner, B. A. (2016). Garner’s Modern English Usage (4th ed.). Oxford University Press.