These two forms of relation open linguistics up to phonology, morphology, syntax and semantics. Take morphology, for example. The signs "cat" and "cats" are associated in the mind, producing an abstract paradigm of the word forms of "cat". Comparing this with other paradigms of word forms, we can note that in the English language the plural often consists of little more than adding an "s" to the end of the word. Likewise, in syntax, through paradigmatic and syntagmatic analysis, we can discover the grammatical rules for constructing sentences: the meaning of "je dois" ("I should") and "dois je?" ("Should I?") differ completely simply because of word order, allowing us to note that to ask a question in French, you only have to invert the word order. A third valuation of language stems from its social contract, or its accepted use in culture as a tool between two humans.