Declension is a change in cases and numbers of nouns. There are three types of declination. In addition, there are divergent (ten nouns of the average gender, ending in -me, as well as the words daughter, path, mother, child) and non-declining nouns (foyer, metro, cafe, radio, show).
Non-declining are called nouns, which in all cases have one form: I see a coat (v. P.), I admire a coat (t. P.).
Tilted Nouns :
1) words borrowed from other languages that end in a vowel and indicate inanimate objects: cocoa, depot, coat, movie, purse, aloe, taxi, coffee.
2) words borrowed from other languages that call male and female representatives and end in a vowel: dandy, attache, impresario, lady.
3) words borrowed from other languages, denoting animals: kangaroos, chimpanzees, cockatoos;
4) female foreign names and surnames that end in a solid consonant: Carmen, Helen, miss, madame, Finkelstein;
5) foreign words that call geographical objects: Helsinki, Baku, Calais, Toronto.
6. Russian surnames, which are a form of the genitive case and many others numbers: Durnovo, Khitrovo, Polish, Twisted.
7. Ukrainian surnames at -co: Korolenko, Franco, Shevchenko, Oleshko;
8) abbreviations are also indeclinable nouns, examples: Germany, Moscow State University, UN, RF, USA.
When combining non-declining nouns with other words, the form of their case can be determined by the construction of the whole sentence (for example, in the hall there was an old pier glass (named after them), or by the end of adjectives that are consistent with these non-declining nouns: Maxim wrapped his neck in a warm muffler ( tv p)
Inanimate non-declining nouns are attributed mainly to the middle gender: sweet popsicle, woolen muffler, scheduled interview, metro in the capital. The unswerving noun coffee (black) refers to the masculine gender, while Avenue and Kohlrabi to the feminine.
Animate borrowed nouns refer to g. p. if they call females (frau, madame, miss, lady), and m. if they call animals and males (chimpanzees, entertainers, dandies, attaches, cockatoos).
The gender of non-declining nouns, which denote the names of geographical objects, is determined by the gender of those common nouns with which these names can be replaced: Gaborone (city) - the indeclinable noun of the masculine, Missouri (river) - of the feminine;
The gender of complex words and abbreviations is most often determined by the gender of the main (reference) word when decoding: LFK - physiotherapy exercises - feminine, as the main word is feminine; KGB - State Security Committee - masculine, as the main word is masculine; BelAZ - (Belarusian Automobile Plant) - masculine, as the main word is masculine, etc.
Since non-declining nouns are borrowed from other languages, their spelling should be checked in spelling dictionaries.