Presume vs. Assume: How to Choose the Correct Word

Among their other definitions, presume and assume both mean "to suppose." However, the two terms suggest different levels of confidence, so they aren't interchangeable. Here's how to use these words correctly.

How to Use Presume

Presume means to suppose, to take for granted, or to take something on (such as a dare or an attitude). The word stems from a Latin verb meaning to take upon oneself, to take liberty, or to take for granted.

When presume is used to mean “to suppose,” the implication is that the supposition is believed to be true based upon proof of evidence or probability. While it does not imply that the supposition is necessarily correct, it does suggest that the speaker (the person doing the presuming) has based their view on available proof.

One interesting usage of "presume" is the familiar legal phrase “presumed innocent until proven guilty.” Even though there is no evidence of an individual's innocence, the court system intentionally presumes their innocence at the beginning of a trial. In other words, the trial begins with the confidently-held belief that the defendant is innocent. Consequently, the burden of proof falls on the prosecution to demonstrate the defendant's guilt.

How to Use Assume

Assume means to suppose, to take for granted, or to take something on (such as a role). This definition overlaps significantly with that of presume, but there are some meaningful distinctions.

When assume is used to mean "to take something on," it refers to taking on a new responsibility, a task, or a role. For instance, you might assume a false identity, or assume the position of club secretary.

When assume is used to mean “to suppose,” the implication is that the speaker does not have reason or evidence to back up their assumption.

Examples

Peter sent his friend a letter three weeks ago, but still hasn't received a response. He assumed that the letter got lost in the mail.

Peter has no evidence to back up his belief that the letter was lost in the mail; thus, he is making an assumption.

Sally heard a knock on the door. "I presume that's Mr. Jones," she said. "I invited him over for dinner this evening."

Sally is confident in her statement. She invited Mr. Jones over for dinner, so she has solid evidence that he is the person knocking on her door.

Sarah is a vegan, so I presume she won't want any of this cheese pizza.

In this sentence, the speaker is using evidence to make an educated guess that Sarah will not want pizza based on previous knowledge of her diet,

Abraham Lincoln assumed the position of president on March 4, 1861.

Here, assume is used to indicate that the subject of the sentence is taking on a new role.

How to Remember the Difference 

Struggling to remember when to use each word? Keep in mind that "presume" and "proof" start with the same two letters. To presume something is to suppose that it is true based on proof (or the belief that there is proof), whereas assumptions are not based upon any evidence or proof.