Agglutinative language
An agglutinative language is a language in which the words are formed by joining morphemes together. This term was introduced by Wilhelm von Humboldt 1836 to classify languages from a morphological point of view. It was derived from the Latin verb agglutinare, which means "to glue together".
An agglutinative language is a form of synthetic language where each affix typically represents one morpheme (unit of meaning, such as "diminutive", "past tense", "plural", etc.), and bound morphemes are expressed by affixes (and not by internal changes of the root of the word, or changes in stress or tone). Besides, and most importantly, in an agglutinative language affixes do not become fused with others, and do not change form conditioned by others.
Synthetic languages which are not agglutinative are called fusional languages; they sometimes combine affixes by "squeezing" them together, often changing them drastically in the process, and joining several morphemes in one affix (for example, a single short verbal suffix means "past tense, perfect aspect, first person singular").
"Agglutinative" is sometimes used as a synonym for synthetic, although it technically is not. When used in this way, the word embraces fusional languages and inflected languages in general. It is also worth noting that the distinction between an agglutinative and a fusional language is often not a sharp one. Rather one should think of these as two ends of a continuum, with various languages falling more toward one end or the other.
Examples of agglutinative languages are Uralic Languages, Altaic languages, Japanese, Korean, Dravidian languages, Inuktitut, Swahili, Malay and to a lesser extent German, Dutch and Esperanto. In the past most of Iran and the near east also spoke such languages, like Sumerian, Elamite, Hurrian, Urartu, Hatti, Guti, Lullubi, Kassite.
Agglutinative languages are not entirely grouped by the family (although Finnish and Hungarian are related, as are possibly Japanese and Korean). Rather, convergent evolution had many separate languages develop this property.
Agglutinative languages tend to have a high rate of affixes/morphemes per word, and to be very regular. For example, Japanese has only three irregular verbs (and not very irregular), and Turkish has only one.