What is the lingustic term for a language's usage conventions?

Question

Every language has usage conventions that cannot be deducted from a basic dictionary. For example, to describe highly concentrated tea, English speakers will usually use "strong tea". Is there a scientific/linguistic term for such conventions/word pairings?

Answer 1

The word you are looking for is collocation:

In corpus linguistics, a collocation is a sequence of words or terms that co-occur more often than would be expected by chance. In phraseology, collocation is a sub-type of phraseme. An example of a phraseological collocation, as propounded by Michael Halliday, is the expression strong tea.
_{Wikipedia: Collocation}

The right dictionary to use in this case is a collocation dictionary, such as OZDIC. Alternatively, several Ngram tools can be used for this: searching *_ADJ tea in Google Ngrams or _j* tea in a BYU corpus will tell you which adjectives are used before tea.