The system of personal pronouns in Vietnamese language is a very complex one. There is not a set of general personal pronouns in Vietnamese like it is in English (I, you, he, she, we, they). The personal pronouns in English can be used freely without external non-linguistic connotations. I can say that every time my students use personal pronouns (especially "he" and "she" and also "my" and "your") they make mistakes. I always have to say “It is about your father, your father is a man, why are you using ‘she’?”.
Vietnamese language uses plural markers and specific personal pronouns to express an exclusive (or inclusive) distinction.
"Chung toi" expresses the exclusive "we" (plural marker + I) – This "we" includes the speaker and others but excludes the listener.
"Chung ta" expresses the inclusive "we" (plural marker + we) – This "we" includes the speaker, the listener, and possible other people.
In Vietnamese, personal pronouns "I" and "you" are definitely completely different than what they are in English. Although this difference doesn’t lead to direct mistakes, it leads to indirect mistakes.
Certain pairs of pronouns for "I" and "you" indicate the relative social status of the speaker, and listener and there are respectful pronouns used for older people. Words like grandfather, aunt, elder sister etc are widely used as personal pronouns. To form the plural form for these Vietnamese personal pronouns, Vietnamese makes use of plural markers.
The use of such personal pronouns will be determined by extra-linguistic factors such as: status, familiarity, age etc.
Vietnamese also makes use of kinship terms within the extended family to refer to oneself, the listener, or the person spoken about.
Below is an example to exemplify the complex usage of Vietnamese personal pronouns (in this case it is all related to the age and relationship):
Anh = you (for an older man)
Em = you (for younger man or woman)
Me (35 years old), my wife (41 years old), my wife’s sister (37 years old), husband of my wife’s sister (45 years old). Although the husband of my wife’s sister is 10 years older than me, I still call him em (em = you ‘for younger man’). That is because my wife is older than her sister (who is his wife).
As you can see, the usage of personal pronouns in Vietnamese is very complex and it depends on many factors.
Not long time ago, a new personal pronoun has been introduced by political development. The pronoun "dong chi", which means "comrade", has been introduced and the connotation of some existing pronouns have changed.
Most of the learners of English use word by word translation when they are speaking. Vietnamese learners of English can’t do that since their language has such big differences comparing it to English. I believe this is one of the factors that leads to speaking mistakes.