All languages have something in terms of their grammar or vocabulary that if one understands well, communicating becomes much better and easier. Azerbaijani has two of them. One is the rule of harmony and the other is the system of endings or suffixes.
The Rule or Law of Harmony defines what vowels follow one another in words and how they do that. Understanding it is very important because it helps one to know why most suffixes have two or four forms, and what form goes with what word. It also gives you clues about the origin of words which matters when you are not sure whether a suffix should be joined at the end of word or at the beginning. As an example let’s look at the plural ending -lar, -lər.
Examples: Kitablar = books. Evlər = houses. How about the plural of “dahi” (genius) does it take “-lar” or “-lər”? The only way to find out that is to learn the rule of harmony.
Suffixes matter too due to the fact that almost all words connect and make sentences through them. Even the simplest possible sentences require suffixes and it is common for a word to take three or even four endings. Unless you know suffixes and their features it might be difficult for native speakers to understand you. Sometimes, by adding one or two suffixes to a word you can express a whole sentence. Here is an example.
Biz = we
Biz+im = our
Bizim+ki = ours (as in “this book is ours”)
Bizimki+lər = our (indicates plurality of objects that belong to us as in our books)
Bizimkilər+dən = from ours
Bizimkilərdən+dir = It is from us. (It is from that which belongs to us.)
Bizimkilərdəndir+mi = Is it from us? (Is it from that which belongs to us?)
We have one root and six endings in this word.
So, learn these two well and Azerbaijani will become easy.