1. 17th and 18th centuries
1.1. I. Komensky, W. Leibnitz
1.1.1. had pointed to the existence of some common (mainly lexical) features in different languages
1.2. the Frenchmen Claude Lancelot and Antoine Arnaud
1.2.1. the first ever attempt (thought quite naive) to create a grammar on "common in all languages principles"
1.2.2. Universal or Rational Grammar (Pour Royal, 1660)
2. 19th century
2.1. Frederick Schlegel
2.1.1. the first linguist to have made a scientific approach to the regular Contrastive study of structurally different languages
2.1.2. On the ground of a thorough study of ancient Indian and modern Chinese, Polynesian, Turkic and the major West-European lan-guages F. Schlegel singled out among them two clearly distin-guishable groups
2.1.2.1. affixal languages
2.1.2.2. inflexional languages
2.2. August Schlegel
2.2.1. singled out, on the basis of the same morphological criterion, three typologically common groups of languages
2.2.1.1. a) those without any grammatical structure, as they were called
2.2.1.2. b) the affixal languages
2.2.1.3. c) the flexional languages
2.3. Wilhelm Humboldt
2.3.1. the father of typology as a new branch of linguistics
2.3.2. had studied a great number of languages including those of Poly-nesia and American Indians on the basis of the same morphological criterion
2.3.3. grouped all known to him languages into the four classes
2.3.3.1. 1) the isolating languages, which are devoid of the form-building morphemes (like Chinese)
2.3.3.2. 2) the agglutinative languages (like those of the Turkic group)
2.3.3.3. 3) the flexional languages (like the In-do-European or Semitic languages)
2.3.3.4. 4) the incorporating languages of the American and Indians
2.4. Franz Bopp
2.4.1. had introduced a hitherto unknown approach to the typolog-ical investigation of languages on the basis of their syllabic root morphemes structure
2.4.2. succeeded and singled out three typologically distinguishable lan-guage types
2.4.2.1. 1) the language type with the root morpheme consisting of one syllable only (the so-called monosyllabic languages)
2.4.2.2. 2) the language type in which the root morpheme can combine with other roots and affixal morphemes (like in most Indo-European lan-guages)
2.4.2.3. 3) the language types with disyllabic and even trisyllabic root word-structures (as in Semitic languages).
2.5. H. Steinthal
2.5.1. the inner form of the word is the most important part
2.6. F. N. Finck
2.6.1. suggested two more criteria for the typological classification of different languages
2.6.2. The first of these was based on the correlation between the solid (unbreakable) word structure and the fragmentary (breakable) word structures.
2.6.3. The second criterion was based on the type of concord and the manner of its realisation
2.6.4. had singled out eight main types of languages
2.6.4.1. 1) the subordinating word-type languages (like present-day Turkish)
2.6.4.2. 2) the incorporating word-type languages with the most extended word structures (as in the language of Greenland inhabit-ants
2.6.4.3. 3) the regulating type languages having a rather weak connection between the auxiliary words and affixes as in the Subia language (Bantu language family)
2.6.4.4. 4) the isolating root languages (like Chinese)
2.6.4.5. 5) the isolating stem languages (represented by the Samoa language)
2.6.4.6. 6) the root inflected language type (represented by Arabic)
2.6.4.7. 7) the stem inflected language type (like Greek)
2.6.4.8. 8) the group inflected language type (like Georgian).
3. 20s - 30s of the 20th century
3.1. P. Richter and O. Barannykov
3.1.1. pointed to many Sanskrit words being of common, approximately the same or absolutely the same lingual form (sounding).
3.1.2. a short list of several nouns, verbs, numerals and other parts of speech below leaves no doubt whatsoever of their being once of genealogically common source of origin.
4. 20th century
4.1. American linguist E. Sapir
4.1.1. criticised the 19th century typological classifications of languages and the evolutional approach to the development of different lan-guage types
4.1.2. came to the conclusion that some languages, distant in location, could in the course of their development acquire common fea-tures and thus move to a common model and language type
4.1.3. the first to treat a language material as a system
4.1.4. acknowledged the typological nature of language development as well as the possibility of establishing the structural types of lan-guages in accordance with the following three criteria
4.1.4.1. 1. The degree of cohesion between the root morphemes and the affixal morphemes of word-forming nature in a word.
4.1.4.2. 2. The degree of synthesis i.e. the ability of a word to combine and express different lexical and grammatical meanings (as in flexional languages).
4.1.4.3. 3 The nature of grammatical processes by means of which the morphemes are joined in the word (i.e. isolation, agglutination or symbolisation).
4.1.5. suggested four basic types of languages
4.1.5.1. 1) the type of simple purely relational languages in which the syntactic relations are realised without the help of affixal morphemes (as in Chinese)
4.1.5.2. 2) the complicated purely relational type languages in which the syntactic relations can be realised with the help of affixes and without their help (as in Turkish)
4.1.5.3. 3) the simple mixed-type relational languages, realising their syntactic con-nections both by means of agglutination or by means of fusion (as in French)
4.1.5.4. 4) the complex mixed relational type languages in which the meanings of root morphemes may be changed with the help of affixes or inner alterations (like in Latin or in present-day English)
4.2. the Prague school linguists V. Skalička, V. Mathesius, I. Levy, N. S. Trubetskoy
4.2.1. N. S. Trubetskoy on the other hand has elaborated typology of phonemic and morphophonemic systems of languages based on oppositions
4.3. O. Isachenko
4.3.1. investigated the Slavonic languages on their quantitative represen-tation of vowels and on the musical accent in words and b) on the existence or non-existence of palatalised consonants
4.3.2. two types of languages have been identified
4.3.2.1. 1) The vocalic type languages, like Serbian, Croatian and Slo-venian, in which
4.3.2.1.1. a) some consonants have historically changed into vowels and some have become syllable forming /r, l/ as in trg, vlk etc.
4.3.2.1.2. b) languages in which there occurs an insertion of vowels between consonants
4.3.2.1.3. c) languages in which the double consonants have reduced to single consonants
4.3.2.2. 2) The consonantal type languages whose characteristic features are
4.3.2.2.1. a) the existence of the binary opposition of palatalised consonants versus non-palatalised ones
4.3.2.2.2. b) the loss of the syllable forming consonants
4.3.2.2.3. c) the retention of double consonants