Philosophy of language is the reasoned inquiry into the nature, origins, and usage of language. As a topic, the philosophy of language for analytic philosophers is concerned with four central problems: the nature of meaning, language use, language cognition, and the relationship between language and reality. For continental philosophers, however, the philosophy of language tends to be dealt with, not as a separate topic, but as a part of logic, history or politics. (See the section "Language and Continental Philosophy" below.)
First, philosophers of language inquire into the nature of meaning, and seek to explain what it means to "mean" something. Topics in that vein include the nature of synonymy, the origins of meaning itself, and how any meaning can ever really be known. Another project under this heading of special interest to analytic philosophers of language is the investigation into the manner in which sentences are composed into a meaningful whole out of the meaning of its parts.
Second, they would like to understand what speakers and listeners do with language in communication, and how it is used socially. Specific interests may include the topics of language learning, language creation, and speech acts.
Third, they would like to know how language relates to the minds of both the speaker and the interpreter. Of specific interest is the grounds for successful translation of words into other words.
Finally, they investigate how language and meaning relate to truth and the world. Philosophers tend to be less concerned with which sentences are actually true, and more with what kinds of meanings can be true or false. A truth-oriented philosopher of language might wonder whether or not a meaningless sentence can be true or false, or whether or not sentences can express propositions about things that do not exist, rather than the way sentences are used.