Comprehensible input glossary

Read “in Krashen's theory” carefully. He uses acquisition and learning in a specific way. Other authors can use learning as a general word for language development. A learner who says they learned a word has not necessarily made a claim about Krashen's distinction. The same care applies to immersion: a school programme and an informal media habit are different settings.

The primary sources below support the research terms. Practical terms such as input hours and sentence mining describe activities, not validated measures of proficiency. Community labels such as superbeginner do not have a single standard level across channels or apps.

Comprehensible input

Spoken or written language whose message a learner can understand, with context or support when needed.

Also called: CI

You understand it because of context, pictures, gestures, simple speech or background knowledge. Stephen Krashen made the term famous in the late 1970s and early 1980s.

What is comprehensible input?

Input hypothesis

Stephen Krashen's claim that people acquire a language in one way: by understanding messages in it.

It is one of the five hypotheses of his Monitor Model. It also says that speaking is a result of acquisition, not its cause.

Krashen's input hypothesis

i+1

Krashen's shorthand for input containing structures beyond current competence: i is the current stage, and +1 is the next stage.

Krashen argued that you do not need to aim input at i+1 on purpose. If you understand enough varied input, the next structures appear in it naturally. Critics say the idea is hard to measure.

Acquisition

In Krashen's theory, the subconscious process of picking up a language by understanding it, similar to how children learn their first language.

Acquired knowledge feels like intuition: you know that a sentence sounds right without being able to name the rule.

Learning

In Krashen's theory, conscious knowledge about a language, such as grammar rules you can explain.

Also called: Conscious learning

Krashen argued that learned knowledge does not turn into acquired knowledge. Many researchers disagree with this strict separation.

Monitor

In Krashen's theory, the use of consciously learned rules to check and correct what you say or write.

Krashen said the monitor works only under certain conditions: you have time, you are thinking about correctness, and you know the rule. Writing and exams meet these conditions more often than fast conversation.

Monitor Model

The name for Krashen's group of five hypotheses: acquisition–learning, monitor, natural order, input, and affective filter.

The five hypotheses explained

Natural order

In Krashen's model, the claim that some grammatical features develop in a similar order that is not simply the teaching order.

The evidence came from 1970s studies of English grammatical endings, such as Dulay and Burt (1974). Later researchers questioned how general the order is.

Affective filter

Krashen's idea that anxiety, low motivation or low self-confidence act like a mental block that stops input from being acquired.

The model favours relaxed, interesting, low-pressure input. The filter is a theoretical explanation, not a directly measured barrier. Do not blame a learner's feelings when a method does not meet their needs.

Silent period

A time at the start of learning when a learner listens and understands but says little or nothing in the new language.

Researchers observed it in some children who moved to a new country. Online, the term often means a deliberate choice to delay speaking. Krashen saw it as natural, not as a rule that everyone must follow.

Output

Speaking or writing in the language you are learning.

Also called: Comprehensible output

Merrill Swain's 1985 chapter argued for a role for comprehensible output. Later work developed the ideas that output can reveal gaps, test ideas, and support reflection on language.

The output hypothesis

Interaction hypothesis

Michael Long's idea that conversation helps acquisition, because speakers adjust their language and give feedback when someone does not understand.

Also called: Negotiation of meaning

Asking "Sorry, what do you mean?" and hearing a simpler version is an example of negotiation of meaning.

Noticing

Richard Schmidt's idea (1990) that learners must consciously notice a feature of the input for it to become intake.

Also called: Noticing hypothesis

It suggests that simply hearing a form is not always enough. Attention matters.

Crosstalk

A conversation in which a partner uses the language you are learning and you reply in a language you speak well, or with gestures and drawings.

It gives you interactive, comprehensible input before you can speak much. The term is common in the Automatic Language Growth (ALG) community and among self-taught learners.

ALG (Automatic Language Growth)

An approach developed by J. Marvin Brown at the AUA Language Center in Bangkok, which says adults should acquire a language through a long period of understanding before they try to speak.

Also called: Automatic Language Growth

ALG goes further than Krashen. It claims that early speaking and conscious study can harm long-term results. These claims rest mainly on program experience, not controlled research.

ALG and the input-only debate

Superbeginner

Input made for people who know almost nothing of a language: very slow, simple speech supported by pictures, drawings and gestures.

Native content

Material made for native speakers, such as TV series, podcasts and YouTube videos, rather than for learners.

It provides comprehensible input when you can understand its message, with support if needed. A familiar topic, pictures, or captions can make a difference.

Comprehensible input vs immersion

Graded reader

A book written or adapted for learners at a specific level, with a limited vocabulary and simpler grammar.

Extensive reading

Reading a lot of easy text quickly, for meaning and enjoyment, with few or no dictionary lookups.

Studies such as the Fiji "book flood" (Elley and Mangubhai, 1983) are often cited as evidence for its benefits.

Intensive reading

Reading a short, harder text slowly and in detail, looking up words and studying the grammar.

It complements extensive reading. One builds detail, the other builds volume and fluency.

Input hours

The total time a learner has spent listening to and reading the language they are learning.

Many self-taught learners track their hours. Hour-based level guides from online programs are estimates, not research results.

Sentence mining

Collecting sentences from your input that contain one new word or structure, then reviewing them, often as flashcards.

SRS (spaced repetition system)

Software that schedules repeated reviews of items such as words or sentences over time.

Also called: Spaced repetition

Anki

A popular flashcard program that uses spaced repetition. Many learners use it for sentence mining.

Shadowing

Repeating audio aloud immediately after you hear it, to practise pronunciation and rhythm.

It is an output technique. Some input-focused learners add it later, once they understand the audio well.

Immersion

Being surrounded by a language, for example by living in a country where it is spoken or studying school subjects in it.

Immersion gives a lot of input, but not all of it is comprehensible.

Comprehensible input vs immersion

TPR (Total Physical Response)

A method developed by James Asher in the 1960s in which learners respond to spoken commands with physical actions, such as "stand up" or "touch your nose".

Also called: Total Physical Response

TPRS

A classroom method developed by the Spanish teacher Blaine Ray from TPR, in which the teacher and class build a story together through many simple questions, then read it.

Also called: Teaching Proficiency through Reading and Storytelling

Natural Approach

A classroom method described by Stephen Krashen and Tracy Terrell (1983) that starts with listening and understanding and lets speech develop later.

Four strands

Paul Nation's framework for a balanced course: meaning-focused input, meaning-focused output, language-focused learning, and fluency development.