The verb to be (for the ´is´ in English) is handled in a special way, it is different from the other verbs. This is also the case in Turkish, the use of the verb to be is very unique. Unlike all the other verbs, to be is expressed with suffixes. It can be in one of present tense or past tense. Let´s see it in present tense and past tense for different cases of personal pronouns.

NOTE 1

For the third person of the present tense to be, there are two cases. One with no suffix and one with -dir. If you are making a personal statement or you are talking in a casual way, you use the no suffix case. However, if you want to make a definitive or informative statement like one in an encyclopedia, you use the suffix -dir. Both have the same meaning, and sometimes can be used interchangeably. Let´s see examples to this.

This house is very big. --> Bu ev çok büyük.

That is my house. --> O benim evim.

He is a student. --> O bir öğrenci.

Spider is an animal. --> Örümcek bir hayvandır. (The -dir case is used since this is an informative statement)

Sun is larger than earth. --> Güneş dünyadan daha büyüktür. (Again, this is an informative statement)

NOTE 2

When constructing the third person plural past tense form of to be, the suffix -ler can be ommitted in some cases. These are explained below:  

a. Humans or objects that have no individuality take singular conjugation for third person plural. But if the speaker wants to give objects individuality then he can use plural. This would be a poetic sentence. 

b. Humans and other things that have individuality (for instance animals that have names) can take either singular or plural conjugation. Usually if the subject is defined (if we known them) then we use plural conjugation. If the subject is undefined then we use singular conjugation. 

NOTE 3

Since the verb to be is different for each personal pronoun, personal pronouns can be omitted in speech or writing. The meaning of person is given with this verb. To say "I am beautiful." you can use one of:

"Ben güzelim."

"Güzelim.".

Using the personal pronoun adds the meaning of stressing person. We will use the personal pronoun in parenthesis to indicate that it is optional.

Now, let´s see where to be is used:

1. To construct a sentence with a noun or adjective instead of a verb, like in English. The verb to be is the implicit verb here.

   • You are beautiful. --> (Sen) güzelsin.

   • You were beautiful. --> (Sen) güzeldin.

   • This is a house. --> Bu bir ev.

   • That was a house. --> O bir evdi.

    

2. To construct verbs in different tenses, the suffix for each tense is used with either present tense of to be or past tense of to be. Actually, it is present tense of to be in all cases except the regular past tense.