 <p>There are two possible answers to your question depending on your exact intent. If I were to guess, the word you're looking for is: <a href="https://en.wikipedia.org/wiki/Morphology_(linguistics)" rel="nofollow">morphology</a> but it could also be <a href="https://en.wikipedia.org/wiki/Phonology" rel="nofollow">phonology</a>. However, I don't think "phonology" fits your second example.</p> <p>The thing you seem to be describing are various parts of <a href="https://en.wikipedia.org/wiki/Grammar" rel="nofollow">grammar</a>. Grammar is the study of <a href="https://en.wikipedia.org/wiki/Syntax" rel="nofollow">syntax</a>, phonology and morphology.</p> <p>Syntax describes the general structure of the language. How words fit together.</p> <p>Phonology describes how sounds fit together in the language. How many vowels there are, the consonants, the types of consonants etc.</p> <p>Morphology describes how words are formed in the language. Does the language modify words with tenses? Does the language modify words with gender? Does the language not modify words at all but instead use other words? etc.</p>