You are tall. --> Sen uzunsun.

My question is that why we used sun instead of sin, as as this is not i -type suffix to.

reason for this??

Thanks in anitcipation!

because of vowel harmony you can read about it with a search on tc

http://www.turkishclass.com/turkish_lesson_59

but as this is a hard word there might be "ı" instead of u. what you say??

If the first syllable of the word has a flat vowel (a,e,ı,i), other vowels of the word should be flat vowels too.

empty???? necla!!!

When you check your vowel harmony,  always focus on the very last vowel of  the word. 

Here our word is "uzun" , what is the last vowel of it ?  it is "u". So take "u" 

The suffix you want to add is second singular person [you] , so  , we have 4 option to choose for, 

sın

sin

sun

sün

and  which one would be harmonic with "u"  ? , Yes,  with given four options , it is "sun".

u ----> u  

   so,  you can attach it onto the word now.

   Uzun +   sun  ===>  Uzunsun  [ You are tall]

===================================

Another example ;

We want to say   " You are  Kashf-ul  mean  " 

what is the last vowel  in  Kashf -ul   eman      ?  

     it is  "a"

     going back to our options ;  sın

                                                 sin 

                                                 sun

                                                 sün

a ---->  i     NO

a ---> ı        YES

a  ---> u      NO

a -----> ü     NO 

Kashf -ul   eman  + sın   ----->  Kashf-ul   emansın.   ---->  You are  Kashf-ul  eman.

If  the last vowel of the word  is   a  or  ı    ---->    sın         [ Oradasın,  [Sarısın ] 

                                                     e  or  i   ---->    sin           [ Öğretmensin ,  [ İşçisin  ]

                                                     u   or  o   ---->  sun       [ Uzunsun] ,  [ Japonsun ]

                                                     ü  or   ö  ---->   sün        [ Gürcüsün ], [ Dansözsün ]    

• a or ı may be followed by a or ı
• o or u may be followed by u or a
• e or i may be followed by e or i
• ö or ü may be followed by ü or e

here are three rules of vowel harmony:

1. Back vowels are followed by back vowels, front vowels are followed by front vowels. Do not cross the back/front boundary.
2. Unrounded vowels are followed by unrounded vowels.
3. A rounded vowel may be followed by a mix of rounded closed and unrounded open vowels.

Look kash-ul-eman. Dont try to learn every principle about Turkish grammar. Even I dont remember the minor vowel harmony principles now. But I still talk properly. Read a lot and you will learn to use which form of suffix without knowing the minor vowel harmony principles.

• a or ı may be followed by a or ı
• o or u may be followed by u or a
• e or i may be followed by e or i
• ö or ü may be followed by ü or e

here are three rules of vowel harmony:

1. Back vowels are followed by back vowels, front vowels are followed by front vowels. Do not cross the back/front boundary.
2. Unrounded vowels are followed by unrounded vowels.
3. A rounded vowel may be followed by a mix of rounded closed and unrounded open vowels.