Some interesting facts about Vietnamese

Here is a collection of interesting facts about the language of Vietnamese (tiếng Việt) that I just found out when talking to my friends, who are all Europeans, in Bonn (Germany). 

1. In Vietnamese, grandson and nephew are called the same (cháu trai). Similarly, granddaughter and niece are also called the same (cháu gái). 

2. In Vietnamese, you can use the same pronoun "em" to call your younger sibling, no matter whether it is your younger brother or your younger sister. Similarly, this pronoun can be used to call someone who is just a few years younger than you, no matter whether this person is a man or a woman. 

3. However, when referring to your older sibling, you must use the pronoun "anh" to call your older brother and the pronoun "chị" to cold your older sister. Similarly, you can use the pronoun "anh" to call a boy who is just a few years older than you and the pronoun "chị" to call a girl who is just a few years older than you. 

4. The mathematical field of Algebra is called "Đại số". When separating this word into "Đại" and "số", it means big numbers, since "Đại" means big in "Hán Việt" (Sino-Vietnamese) and "số" means "number". However, according to my friend, Lê Xuân Hoàng, "Đại" also means representing (something), thus the Vietnamese word for Algebra means that this subject uses symbols to represent numbers. 

5. In Vietnam(ese), you learn about functor (hàm tử) not only in the mathematical theory of category but also in History and Literature. In History, you learn about Hàm Tử when talking about the battle between the kingdom of Đại Việt (modern-day northern Vietnam) and the Yuan dynasty. In Literature, you learn about Hàm Tử when reading the poem "Bình Ngô đại cáo" written by Nguyễn Trãi, which was about the battle mentioned in the previous sentence. 

6. When talking about fractions in Vietnamese, the term "numerator" (tử số) can be understood as the son/daughter and the term "denominator" (mẫu số) can be understood as the mother, since "tử" means son/daughter and "mẫu" means mother in Sino-Vietnamese. 

7. Meanwhile, "tử" (also) refers to someone's death and "sư" refers to teachers in Sino-Vietnamese. The concatenation of these two words yields "sư tử", which means lions. Therefore, there is a joke which says that a student might cry when seeing a lion because it refers to the teacher's death. 

8. My family name is Trần, the second most popular family name in Vietnam, which also means top or ceiling. There are also many other (popular) family names that have a meaning in Vietnamese. For example, Ngô, the family name of the Field medalist Ngô Bảo Châu, means "corn" in Sino-Vietnamese. Lê, which is the third most popular family name in Vietnam and the family name of many famous Vietnamese mathematicians such as Lê Văn Thiêm, Lê Dũng Tráng, also means pear, a type of fruit. There is even the family name "Võ", which means martial art. (At least) two of my friends during my undergraduate study have this family name, and they are now pursuing graduate studies in Mathematics. One of them is a PhD student at Purdue University, and the other one is a PhD student at Houston University. 

9. In Vietnamese, some mathematical terms such as centralizer, annihilator, ... end with "hóa tử". To a certain extent, "hóa tử" means "become dead". 

10. In English, you might add the prefix -ize to an adjective/property to refer to the action of making something have that property. In Vietnamese, the corresponding word that must be added is "hóa". Meanwhile, "hóa" also means the subject of Chemistry. 

11. In Vietnamese, winning and the action of using a brake to go slower or stop are both called "thắng". Thắng can also be the name of a person. While this name is rather for man, but it is normal if we meet a woman with this name. One of the most famous women with this name is Võ Thị Thắng. 

12. In Vietnamese, Italy (Ý) also means "idea". Therefore, when we talk about ideas via Messenger, the web/application might think that we talk about Italy and, as a result, tells us to use Italy's flag instead. Similarly, Germany (Đức) refers to moral values in Sino-Vietnamese and England (Anh) is just the same as the pronoun that is used to call your older brother that is mentioned in 3. 

13. When referring to half of something, we might use the word "semi" in English. In (Sino)-Vietnamese, it is the word "bán", which also means selling something. 

14. Water and nation are both called "nước". The same word can be used to call a play/move in chess or other similar games. 

15. Cell and umbrella are both called "ô". There is also another word "dù" that can be used to call the umbrella. When "dù" is between two statements/claims, it means "although". 

16. When talking about kilogram in brief, Vietnamese people use the word "kí", but the word "kí" also have many other meanings: 
   - To sign in (a contract, for example)
   - To slightly hurt one's head (e.g. "Tao kí đầu mày bây giờ.")

17. In southern area (Hồ Chí Minh City, my city, for example), the number two is used to call the oldest children/sibling in a family, the number three is used to call the second oldest children/sibling in a family, and similarly, for each i, the number (i + 1) is used to call the i-th oldest children/sibling in a family. For example, I have one older brother, thus three is used. Since my name is Hưng, it is the same as this famous person which appears in a Vietnamese song. 

18. In Vietnamese, the number eight (tám) might refer to a (loud/active) talk between friends (about nonsense things, for example). The word "failure" (thất bại) starts with "thất", which means seven in Sino-Vietnamese. Similarly, "thất" can also be used if you fail to do something. For example, love means "tình" and if you break up with your girlfriend or boyfriend, it means "thất tình" in Vietnamese. The word "ba hoa" refers to a person who shows up too much, but it might also mean three flowers. The number five is called "năm", which is the same as the word used to called a year. We use "chín" to call the number nine, and this word also means that the food/meat is well-done (not rare) or your skill is solid/sharpened. 

19. In Vietnamese, "chai" means bottle, but it also means: 
   - The state of having calluses on your hands or your feet 
   - The fact that a device (e.g. iPhone or laptop) is getting out of battery too fast

20. The word "Từ" in Vietnamese has (at least) four meanings: from, magnetic, word, resignation (from a certain position). This is also the family name of a (small) proportion of Vietnamese people.

21. In Vietnamese, manifold (in differential geometry/topology) and variety (in algebraic geometry, for example) are both called "đa tạp". According to some people, manifold and variety are also called the same in French. "Đa" means multi or many. The Vietnamese word "tạp" means impurity, thus manifold and variety means that there is a too large amount of (possibly toxic) impurity inside a chemical/object. 

22. "Áo dài", which is a traditional cloth in Vietnam and also one of the Vietnamese words that is mentioned in Oxford dictionary, means long shirt, since "dài" means long. 

23. Vietnamese has six different tongues. One of these tongues, "hỏi" is denoted by a stuff that is similar to the question mark (?) and another tongue, "ngã", is denoted by a stuff that is similar to the tilde. These two tongues might seem similar at first, since their differences only lie in how we stress or emphasize when we pronounce. One of my friends often makes mistakes when it comes to these two tongues: instead of putting the "tilde" tongue to get the right word/spelling, he puts the "question" tongue and gets a wrong word/spelling. 

24. In Vietnamese, we have a lot of pronouns for first person singular that mean "I". One of them is "Tao", which is the same as Tao in the name Terence Tao. This is the fact behind various jokes in Vietnamese, for example when people say "Tao kìa" (It's (Terence) Tao if Tao means Terence Tao or It's me if Tao means "I") in Vietnamese, other people will ask "You?". 

25. The Vietnamese word "đồng" has two meanings: first, it represents similarity between things; second, it also means bronze, a kind of metal. 

26. Homology is called "đồng điều" in Vietnamese. While "đồng" means similarity (as mentioned in 25), which is probably the idea behind homology, the Vietnamese word "điều" might have one of the following meanings: cashew, a thing or point (inside a long paragraph, for example). 

27. Austria is also called "Áo" (same as "áo" in "áo dài" mentioned in 22) in Vietnamese. 

28. Belgium is called "Bỉ" in Vietnamese. Meanwhile, the word "bỉ" can also be added after another word to talk about scornful behaviours. There is also a Vietnamese Literary work whose name starts with this word, "Bỉ vỏ", which is written by Nguyên Hồng. As far as I know, "Bỉ vỏ" refers to a female robber/thief. 

29. In Vietnamese, "biến cố" might refer to one of two things: 
   + An incident, which is a (usually sad) event that largely affects one's later life. 
   + An event, in probability.

30. When you talk about subsets in Vietnamese, you might think that a subset is the "child" of a set, since subset is called "tập con". Here, "tập" means set and "con" is the word used to refer to someone's child. As a result, you might think that a supset is the father/mother of a set.