Pseudoscientific[1] language comparison is a form of pseudo-scholarship that aims to establish historical associations between languages by naïve postulations of similarities between them.
While comparative linguistics also studies how languages are historically related, linguistic comparisons are deemed pseudoscientific when they do not follow the established practices. Pseudoscientific language comparison is usually performed by people with little or no specialization in the field of comparative linguistics. It is a widespread type of linguistic pseudoscience.
The most common method applied in pseudoscientific language comparisons is to search different languages for words that sound and mean alike. Such similarities often seem convincing to common folks, but linguistic scientists see this kind of comparison as unreliable for two primary reasons. First, the criterion of similarity is subjective and thus not subject to verification or falsification, which runs against scientific principles. Second, because there are so many words, it is easy to find coincidental similarities.
Because of its lack of reliability, the method of searching for isolated similar words is rejected by nearly all comparative linguists (however, see mass comparison for a controversial method that operates by similarity). Instead, experts use the comparative method. This means that they search for consistent patterns between the languages' phonology, grammar and core vocabulary. This technique helps linguists to figure out whether the hypothesized relatedness really exists.
Certain languages seem to get much more attention in pseudoscientific comparisons than others. These include languages of ancient civilizations such as Egyptian, Etruscan or Sumerian; language isolates or near-isolates such as Basque, Japanese and Ainu; and languages that are not related to their geographical neighbors such as Hungarian.
Fringe and crackpot claims about language display the standard pseudoscientific characteristics discussed many years ago by Martin Gardner (1957) and by numerous observers since then, such as Michael Shermer (2011)