Là (Prep)

Situations

S1: Dũng asks Nam about his decision to quit his job. Nam answers:

Tôi nghĩ là anh đã quyết định đúng.
(I think that you've made the right decision.)

In this situation, anh đã quyết định đúng (you've made the right decision) is what Nam thinks about.

S2: Dũng has run into a technical difficulty. Dũng complains to Nam; Nam says:

Ai cũng biết là vấn đề đó rất phức tạp. Nhưng tôi tin là anh sẽ giải quyết được.
(Everyone knows that that problem is very complicated. But I think that you'll be able to solve it.)

In this situation, similar to in S1, the part after là is the content of biết (to know) or tin (to believe).

Definition

Là, as a preposition, is placed after verbs that convey feelings, consciousness, or speaking such as "to think", "to know", "to speak", "to praise", "to criticize", etc., in order to indicate that what follows these verbs is the content the subject wants to talk about.

  • là and rằng: If after là there is a Subject-Verb structure, là can be replaced by rằng.
[1] Ai cũng nghĩ là / *rằng anh ta.
    (Everyone thinks it's him.)
[2] Ai cũng nghĩ là / rằng anh ta có lỗi.
    (Everyone thinks that he is at fault.)

Combinations

  • Là as a preposition usually goes after the following terms: có thể, có lẽ, hình như, dường như, nghe đâu, nghe nói, có cái, có điều, hóa ra, chẳng qua, chắc là, ai ngờ, dĩ nhiên, etc. For example:
[1] Hình như là trời mưa.
    (It seems to be raining.)
[2] Lâu rồi tôi không gặp cô ấy. Nghe nói là cô ấy về nước rồi.
    (I haven't seen her for a long time. I heard that she went home already.)
[3] Bề ngoài anh ta như thế, ai ngờ là anh ta ăn cắp.
    (With an appearance like that, no one would expect that he is a thief.)
  • ... là ít / ... là nhiều, ... là cùng, etc.: Combinations used to strongly assert something and express the subjective attitude of the speaker.
[4] Lớp này 50 sinh viên là ít.
    (This class has at least 50 students.) (The speaker evaluates the number as likely higher than 50.)
[5] Lớp này 50 sinh viên là nhiều.
    (In this class, there are 50 students at the most.) (The speaker evaluates the number as likely lower than 50.)
[6] Chúng ta nghỉ hè một tháng là cùng.
    (We have one month off at the most.) (The speaker says that one month is the maximum time.)
  • toàn là X / toàn X là X: There is only one type (type X), all are X. This combination also has a subjective nuance.
[7] Lớp này toàn là người Hà Nội.
    (This class is completely made up of people from Hà Nội.)
[8] Chung quanh cô toàn hoa là hoa.
    (There are flowers and only flowers around her.)