In linguistics, a conservative form, variety, or modality is one that has changed relatively little over its history, or which is relatively resistant to change. It is the opposite of innovating forms or varieties, which have undergone relatively larger changes.
A conservative linguistic form, such as a word, is one that remains closer to an older form from which it evolved, relative to cognate forms from the same source. For example, the Spanish word caro and the French word cher both evolved from the Latin word cārum. The Spanish word, which is more similar to the common ancestor, is more conservative than its French cognate.
A language or language variety is said to be conservative if it has fewer innovations (in other words, more conservative forms) than related varieties do. For example, Icelandic is more similar to Old Norse than other languages that evolved from Old Norse, including Danish, Norwegian, or Swedish. Therefore, Icelandic is a relatively conservative language. Likewise, some dialects of a language may be more conservative than others. Standard varieties, for example, tend to be more conservative than non-standard varieties, since education and codification in writing prevent them from changing.
Writing is generally said to be more conservative than speech. That is to say that written forms generally change more slowly than the spoken language does. This helps to explain inconsistencies in writing systems such as that of English; since the spoken language has changed relatively more that the written language has, the match between spelling and pronunciation is inconsistent.
A language may be conservative in one respect while simultaneously innovative in another. The closely related Slavic languages Bulgarian and Macedonian, for example, are innovative in the grammar of their nouns, having dropped nearly all vestiges of the complex Slavic case system; at the same time, they are highly conservative in their verbal system, which has been greatly simplified in most other Slavic languages. English, which is one of the more innovative Germanic languages in most respects, is nevertheless conservative in its consonant phonology, retaining sounds such as (most notably) th which have been altered in other Germanic languages.
Conservative languages are often thought of as being more grammatically (or at least, morphologically) complex than innovative languages. This is largely true for Indo-European languages, where the parent language had an extremely complex morphology and the dominant pattern of language change has been simplification. On the other hand, a number of Arabic varieties commonly considered innovative, such as Egyptian Arabic, have developed a complex agglutinative system of verbal morphology out of the simpler system of Classical Arabic.
See also 
- Trask, Robert Lawrence (2000). The Dictionary of Historical and Comparative Linguistics. London: Routledge.
- Chambers, J.K. (2009). "Education and the enforcement of standard English". In Y. Kawaguchi, M. Minegishi and J. Durand. Corpus Analysis and Variation in Linguistics. Philadelphia: John Benjamins.
- Fromkin, Victoria, Robert Rodman and Nina Hyams (2010). An Introduction to Language. Cengage Learning.