The distinction between a language and a dialect is somewhat ambiguous. Suzette Haden Elgin wrote that while she would consider Navajo (Diné) and Apache to be dialects of the same language, she feels sure that no native speaker of either language would agree. Similarly, Laotian and Thai seem like dialects to outsiders, but for various reasons are thought of as separate languages by their native speakers.

Linguists often say, attributing the idea to Max Weinreich, that the difference is that

a language is a dialect with its own army and navy.

Of course, this would exclude many landlocked languages from the definition. On a less literal level, however, it rings true. Nationalism can contribute strongly to a sense of linguistic identity.

SOURCE: Suzette Haden Elgin, "The Language Imperative"