Spoiler Warning: If you haven't seen Arrival and plan to soon, you might want to save this article for after.

The most exciting thing about Denis Villeneuve’s new sci-fi space-encounter movie isn’t the aliens or the spaceships or the worldwide panic they bring on. It’s the fact that the hero is a linguistics professor!

It’s nice to feel that your seemingly esoteric field is actually the key to saving humankind. Even better if a film about it can get more people interested in the science of language structure. The film’s linguist, Louise Banks, played by Amy Adams, is charged with figuring out the language of the aliens who have landed on earth. She needs to do this in order to find out what they want.

How would one go about decoding a language that nobody knows? Field linguists—those who go out into the world to analyze little-known languages—have developed techniques for doing this kind of thing. The filmmakers consulted with McGill University linguist Jessica Coon, who herself has worked in the field on native languages of Mexico and Canada.

The problem of interpreting an unfamiliar language becomes a lot harder when dealing with creatures that don’t share our human bodies or articulators, much less a common frame of reality or physical environment, but that’s no reason not to start with the basics of linguistic communication that we do have a handle on. Here are four important concepts from linguistics that help Dr. Banks do the job she needs to do in Arrival.

1. THE SWADESH LIST

At one point Colonel Weber (played by Forest Whitaker) asks Dr. Banks why she’s wasting time with a list of simple words like eat and walk when their priority is to find out what the purpose of the aliens’ visit is. A good field linguist knows you can’t just jump to abstract concepts like purpose without establishing the basics first. But what are the basics?

For decades, linguists have used variations on the Swadesh list, a list of basic concepts first put together in the 1950s by linguist Morris Swadesh. They include concepts like I and you, one and many, as well as objects and actions in the observable world like person, blood, fire, eat, sleep, and walk. They were chosen to be as universal as possible, and they can be indicated by pointing or pantomime or pictures, which makes it possible to ask for their words before proper linguistic question-asking has been figured out. Though the movie’s heptapods likely don’t share most of our universal, earth-bound concepts, it’s as good a place to start as any.

2. DISCRETENESS

It might seem that the most important question to focus on when trying to analyze an unknown language is "what does this mean?" For a linguist, however, the most important question is "what are the units?" This is not because meaning is not useful, but because, while you can have meaning without language, you cannot have language without units. A sigh is meaningful, but not linguistic. It is not composed of discrete units, but an overall feel.

The concept of discreteness is one of the basic design features of human language. Linguistic utterances are patterns of combinations of smaller, meaningless units (sounds, or in the movie’s case, parts of ink blots) that reoccur in other utterances in different combinations with different meanings. When Dr. Banks sits down to analyze the circular ink blots the heptapods have thrown out, she marks up specific parts of them. She is not viewing them as analog, holistic pictures of meaning, but as compositions of parts, and she expects those parts to occur in other ink blots.

3. MINIMAL PAIRS

The concept of the minimal pair is crucial for figuring out what the units of a specific language are. An English speaker will say that car, whether it's pronounced with a regular r or a rolled r, means the same thing (even if the rolled r sounds a bit strange). A Spanish speaker will say that caro means something different with a rolled r (caro "expensive" vs. carro "car"). The rolled r in English is just a different pronunciation of the same unit. In Spanish, it’s a different unit.

A minimal pair is a pair of words that differ in meaning because one sound has changed. The existence of a minimal pair shows that the differing sound is a crucial element of the language’s structure. In one scene in the movie, Dr. Banks notes that two ink blots are exactly the same except for a little hook on the end. That’s how she knows the hook does something important. With that knowledge, she can put it in the known inventory of units for heptapod, and look for it in other utterances.

4. THE SAPIR-WHORF HYPOTHESIS

The linguistic current running through the heart of the movie is a version of what’s come to be known as the Sapir-Whorf hypothesis, most simply explained as the idea that the language you speak influences the way you think. This idea is controversial, since it has been demonstrated that languages do not restrict or constrain what people are able to perceive. However, a milder version of the theory holds that language can lay down default ways of categorizing experience that are easily shaken off if required.

We see the extreme version of Sapir-Whorf played out in the way that the perceptive abilities of Dr. Banks are completely transformed by the act of her learning the heptapod language. Her conception of time is altered by language.

The origins of the Sapir-Whorf hypothesis trace back to an analysis by Benjamin Whorf of the concept of time in the Native American language Hopi. He argued that where the linguistic devices of European languages express time as a continuum from past to present to future, with time units like days, weeks, and years conceived of as objects, the Hopi language distinguishes only between the experienced and the not experienced, and does not conceive of stretches of time as objects. There are no days in Hopi, only the return of the sun.

Whorf’s analysis has been challenged by later Hopi scholars, but it is clear that the language does handle the idea of linguistic tense in a way that is difficult to grasp for speakers of European languages. Assuming that that means we live in a different reality with respect to time is taking things way too far. But who ever said the world of fiction wasn’t allowed to take things too far?

If you find the real ideas behind the movie intriguing, or just want to get more familiar with the exciting world of linguist-heroes, check out this collection of real world resources listed by Gretchen McCulloch.