What makes comprehensible input comprehensible? Is that a trick question?
Avoiding unknown vocabulary, or including just a small amount that can be inferred from context; avoiding rare grammatical rules; avoiding stuffing too many clauses into sentences, keeping them short.
Just like a language has a large vocabulary of words of which only a subset is common, a similar observation holds for the grammar rules. Some are used only in very formal/erudite speech or writing. Also, just like your active vocab is not as large as the vocab you understand, the same goes for grammar: you don't wield as many constructs as you grow.
Semantically, avoiding obscure cultural references, culturally rooted unstraightforward metaphors, figures of speech or idioms.
Avoiding difficult topics. E.g. "I have a pen" vs. explaining Karl Popper's logical positivism.
It's much easier to acquire the "household" dialect of a language than to be able to understand news about politics, scientific papers, or literary essays.
Avoiding unknown vocabulary, or including just a small amount that can be inferred from context; avoiding rare grammatical rules; avoiding stuffing too many clauses into sentences, keeping them short.
Just like a language has a large vocabulary of words of which only a subset is common, a similar observation holds for the grammar rules. Some are used only in very formal/erudite speech or writing. Also, just like your active vocab is not as large as the vocab you understand, the same goes for grammar: you don't wield as many constructs as you grow.
Semantically, avoiding obscure cultural references, culturally rooted unstraightforward metaphors, figures of speech or idioms.
Avoiding difficult topics. E.g. "I have a pen" vs. explaining Karl Popper's logical positivism.
It's much easier to acquire the "household" dialect of a language than to be able to understand news about politics, scientific papers, or literary essays.