Prior Knowledge
Reading requires a lot from our brains. We decode out each word, put those words together into sentences and paragraphs, and hold all of the information in our working memory as we go. There is another aspect of reading we do without thinking much about it: activating our prior knowledge.
Prior knowledge is the information we carry around with us, and all the previous experiences we call up when reading. For example, when we read a book about sea turtles, we recall everything we already know about the subject of turtles and related topics like the ocean and reptiles.
Prior knowledge gives us a foundation to build upon, so when we read about a broad topic, like U.S. current events, we don't have to start all over again from the beginning. Just as knowing a bit about each U.S. state helps you to understand a national newspaper, it helps if you already know what a turtle is and what they look like when reading about sea turtles.
When we read a novel, we make connections to what we already know, including connections to other works of literature. Through different reading experiences we develop expectations of specific genres, say, mystery or romance novels, and start to recognize the literary conventions authors use.
Prior knowledge is also particularly helpful when reading historical fiction, where knowing even a little bit about the past can assist you as a reader. Think about how our understanding of the history of slavery in the Southern United States could aid our understanding of books like Mark Twain's The Adventures of Huckleberry Finn, Toni Morrison's Beloved, and Margaret Mitchell's Gone with the Wind, all of which deal with slavery (and slavery's legacy) through very different perspectives.
Context Clues
When faced with a word we don't know, especially when reading, we often use the context in which the word is used to determine its meaning.
Take, for example, this quote from The Adventures of Huckleberry Finn by Mark Twain,
'The Widow Douglas she took me for her son, and allowed she would sivilize me; but it was rough living in the house all the time, considering how dismal regular and decent the widow was in all her ways; and so when I couldn't stand it no longer I lit out.'
You might not have immediately recognized the word 'sivilize' by sight, but if you read it aloud you might notice that it sounds like 'civilize,' which matches the Widow Douglas' plans for Huck. If you didn't know what the word 'dismal' meant, you could look at the rest of the sentence - 'rough living,' 'couldn't stand it any longer' - and know 'dismal' wasn't a good thing.
Context clues provide readers with enough information that they can infer or make an educated guess about the meaning of a word. Often, context clues mean we don't have to check an online dictionary or other reference material, allowing us to continue reading with less disruption.
Here is another example from the novel The Golden Notebook by British writer Doris Lessing:
'I don't think I really saw people then, except as appendages to my needs.'
If you didn't know what 'appendages' meant, you could use the context clues in the rest of the sentence to figure it out. The speaker says she wasn't able to 'see people' except for how they could serve her needs, making an 'appendage' something that is secondary to a primary object.