Function of a Part
How to Decode Why Authors Include Specific Details on the SAT
Track the author’s logic, locate evidence quickly, and sharpen your reasoning.
Evidence-First Reading
Anchor every answer in the exact line that proves it. If you cannot point to the words, it is not the answer.
- Read the question, then scan for the line that directly supports a choice.
- Match wording, not vibe: synonyms are fine, new ideas are not.
- If two answers feel close, eliminate the one with any extra claim.
Why Function of a Part Matters on the SAT
When you encounter a Function of a Part question, the SAT is asking why a specific sentence, phrase, or detail appears in a passage. Several answer choices will sound plausible, but only one correctly explains how that element fits into the author's larger purpose. These questions show up frequently on the SAT Reading and Writing section and reward a particular kind of structural thinking.
Here's the good news: these questions aren't testing whether you understood every word of the passage. They're testing whether you can step back and see how a piece of text fits into the larger argument. That's a skill that, once it clicks, transfers to almost every other reading question type. Students who master this skill often see noticeable improvements in their overall reading score because it trains you to read with purpose, exactly the way the SAT wants you to read.
What Is This Skill?
Every time an author writes a sentence, they make a choice. They could have left that sentence out, replaced it with something else, or moved it somewhere different. Function of a Part questions ask you to figure out why the author made the choice they did. In other words: what job does this specific sentence, phrase, or detail perform within the text?
Think of a passage like a machine with interlocking gears. Each sentence is a gear. A Function of a Part question points to one gear and asks, "What does this gear do for the machine?" It's not asking what the gear is, it's asking what the gear does. That distinction is everything.
Here are some of the most common functions a part of a passage can serve:
- Introduce a claim or thesis, The sentence presents the author's main argument or position.
- Provide evidence or support, The sentence offers a fact, statistic, example, or quotation that backs up a nearby claim.
- Present a counterargument or complication, The sentence acknowledges an opposing view or introduces a tension that the author will address.
- Transition between ideas, The sentence shifts the passage from one topic or perspective to another.
- Qualify or refine a previous point, The sentence adds nuance, limiting or adjusting something stated earlier.
- Illustrate or elaborate, The sentence makes an abstract idea more concrete or vivid through an example or analogy.
Notice that all of these descriptions focus on relationships, how the part connects to what comes before and after it. That relational thinking is the core of this skill.
How the SAT Tests This Skill
On the digital SAT, you'll encounter short passages followed by a single question. When the test is targeting Function of a Part, the question will typically use phrasing like:
- "Which choice best describes the function of the underlined sentence?"
- "The second sentence serves primarily to..."
- "What is the main purpose of the third sentence in the overall structure of the text?"
The answer choices will not simply restate what the sentence says. Instead, they'll describe the sentence's role using structural language: words like "introduce," "counter," "illustrate," "qualify," "support," and "transition." This is why understanding the vocabulary of text structure matters so much, it's the language the SAT uses in its answer choices, and if you're fluent in it, you can eliminate wrong answers much faster.
A common trap is choosing an answer that accurately summarizes the sentence but doesn't describe its function. The SAT is counting on you to confuse what a sentence says with what a sentence does. Keep that distinction sharp, and you'll avoid the most common mistake on these questions.
A Reliable Strategy for Function of a Part
Here's a reliable, repeatable approach you can use every time you face a Function of a Part question. Think of it as a three-step process: Locate, Connect, Match.
- Locate the Part
Read the question carefully and identify exactly which sentence or phrase it's asking about. On the digital SAT, the relevant sentence is often underlined or explicitly referenced ("the second sentence"). Before you even look at the answer choices, reread that sentence and make sure you understand what it's saying on a literal level.
- Connect It to Its Neighbors
This is the most important step. Read the sentence before and the sentence after the one in question. Ask yourself:
- Does this sentence support what came before it? (evidence, example, elaboration)
- Does it shift the direction? (counterargument, contrast, qualification)
- Does it set up what comes next? (claim, thesis, framing)
Think of yourself as a detective examining the relationship between sentences. The sentence doesn't exist in isolation, its function is defined by its context. A statistic placed after a claim is evidence. That same statistic placed at the beginning of a passage might be a hook or an introduction to a problem. Position matters.
- Match to the Best Answer
Now scan the answer choices. Eliminate any option that merely restates the content of the sentence rather than describing its structural role. Then, look for the answer that uses language matching the relationship you identified in Step 2. If you decided the sentence provides evidence for a claim, look for words like "support," "substantiate," or "illustrate." If you decided it introduces a counterpoint, look for "challenge," "complicate," or "counter."
A Quick Self-Check
Before you commit to your answer, try this metacognitive trick: mentally remove the sentence from the passage. What would be lost? If you removed it and the argument would lose its evidence, the function is "to provide support." If you removed it and the transition between ideas would feel abrupt, the function is "to bridge two ideas." What the passage loses when the sentence disappears tells you exactly what the sentence contributes when it's there.
Function of a Part Traps
- Content recap: The choice repeats what the sentence says instead of describing what it does.
- Wrong role: The answer labels the sentence as evidence, contrast, or setup when it doesn't match the neighboring sentences.
Practice Function of a Part with SAT-Style Questions
Note: The passages below are original, SAT-style constructions for practice; any names or details are fictionalized.
Now it's time to put the Locate, Connect, Match strategy to work. For each question below, resist the urge to jump straight to the answers. Instead, identify the sentence in question, examine what comes before and after it, and form your own idea of its function before reading the choices. You'll be surprised how often the right answer jumps out when you do this.
Which choice best describes the function of the third sentence in the text ("This finding...farming")?
Which choice best describes the function of the first sentence in the text ("The novelist...defined")?
Which choice best describes the function of the second sentence in the text ("However...niches")?
Which choice best describes the function of the third sentence ("Importantly...used it")?
Which choice best describes the function of the third sentence in the text ("The banjo...musicians")?
Key Takeaways for Function of a Part
- Function ≠ Content. The most important distinction on these questions is between what a sentence says and what it does. Always ask yourself: what role does this sentence play in the text's structure?
- Context is everything. A sentence's function is determined by its relationship to the sentences around it. Always read what comes before and after the sentence in question.
- Use the "removal test." If you mentally delete the sentence, what does the passage lose? That loss reveals the sentence's function.
- Learn the vocabulary of structure. Words like "support," "qualify," "illustrate," "counter," "introduce," and "transition" appear constantly in SAT answer choices. The more comfortable you are with these terms, the faster you can identify correct answers.
- Watch for signal words. Transition words at the beginning of a sentence, "However," "For instance," "Importantly," "In contrast", are strong clues about function. They often tell you exactly what role the sentence is playing.
Conclusion: The Core Rule for Function of a Part
Function of a Part questions might seem intimidating at first, but they're actually testing something beautifully simple: can you see how a piece of writing is constructed? Every author builds an argument one sentence at a time, and each sentence has a job to do. Once you train yourself to see those jobs, to notice when a sentence is providing evidence, introducing a complication, or bridging two ideas, you're not just answering SAT questions. You're reading the way skilled writers and critical thinkers read.
The Locate, Connect, Match strategy gives you a reliable framework for these questions, but with practice, the process will become intuitive. You'll start noticing sentence functions automatically, in textbooks, articles, essays, even emails. That's the real power of this skill: it doesn't just help you on test day. It changes the way you engage with every piece of writing you encounter.
Keep practicing, stay curious about how arguments are built, and trust that this skill will compound over time. You're building something that goes far beyond the SAT.

