Words within a language are also not completely arbitrary. Speakers of a language are even able to understand many new words which follow the familiar patterns of other words in the language. For eg, consider the word ‘Google’, originating as the proper noun referring to the popular search engine, which many people are still comfortable using as a verb.
We also know when sentences are malformed
The lack of a negative here makes the sentence seem incorrect, even though we lack an explicit reason to point at and say, ‘this is why you cannot do this’.
Many languages (notably excluding English) have honorific systems for their pronouns. It would be a faux pas to say “tu kab record karegi?” to your teacher (and it may or may not get you in hot water).
Deictic (noun form: deixis) terms are those which have only a general meaning out of context, but whose exact intent can only be gathered from context, like “tomorrow” or “there”. Even in context, however, they may not always be clear:
The sentence here is ambiguous, who does ‘voh’ refer to? We might have had a clue to it, if we had referred to ‘Rohan’ as ‘Sharmaji’ perhaps we could’ve been a bit more sure that it was Rohan’s son who was drunk, because we did not use “… veh piiye hue the”.
We often use “common sense” to disambiguate and infer the meaning of a sentence or phrase.
We can guess as to who ‘she’ refers to from what we consider to be obvious, since cows do not usually make monetary transactions, we can safely assume that it was ‘Mother’ who needed the money.
The study of language has long been diachronic, dealing more with the traditional and literary use of language, the origin of words (etymology) etc. We can also look at things synchronically, dealing more with the contemporary use of the language, and what shape it has moulded itself into in the present.