"The boy sees the man."

[capedia]

why it shoud be vale, cant it be vala???

[SprightBark]

Nouns in High Valyrian change their ending depending on their role (case) in the sentence.

With urnes:

• Vala would mean the man is the one who is seeing something.
• Vale would mean the man is the one who is seen.

Both of these mean the same thing ("The boy sees the man"):

• Taoba vale urnes.
• Vale taoba urnes.

Both of these mean the same thing ("The man sees the boy"):

• Vala taobe urnes.
• Taobe vala urnes.

(Even though they mean the same thing when the order is changed, in general stick with the Subject Object Verb word order - the first in each of the pairs I have used as examples.)

Taoba vala urnes would be (mildly) ambiguous as to who is doing the seeing and who is being seen.

There are patterns to these endings. Many singular nouns which end in -a when they are the subject of the sentence (the one doing the verb) will end in -e when they are the direct object of the sentence. There are other patterns too, depending on the ending of the noun in its most basic (nominative singular) form.

Some of this is discussed briefly here: https://wiki.dothraki.org/High_Valyrian_Tutorial#Case