Thanh V. answered • 05/31/19
Native Vietnamese, 20+ Years of Teaching
In Vietnamese, the inflection of a word is counted as part of its spelling, thus every word can be considered as having its own inflection. So the technical answer to your question is: words in Vietnamese do inflect, actually ALL of them inflect, but they do not inflect base on case/time/gender/etc. they inflect base on their own meanings. Example: the following six words, because of their different inflections, have different meanings:
hái (to plug fruits from a tree)
hài (comedy)
hải (sea)
hãi (terrified)
hại (to harm/hurt someone/something)
hai (two)**
**notice that the sixth inflection is one without a special mark, and it is called the "ngang" meaning "flat in tone"
