(only before Sino-Vietnamese numerals) ordinal number marker, used only to mark the generation of a person who shares their name with their parents or grandparents, equivalent to the use of I, II, III, etc. in English.
(only before Sino-Vietnamese numerals, rare) ordinal number marker in general

noun

(Chinese fiction) a younger brother
(slang) a henchman or minion

pron

(Chinese fiction) I; you (refers to the male junior among the speakers)

đệ nhất

đệ nhất
adj

first

đệ nhất phu nhân

đệ nhất phu nhân
noun

First Lady

đệ nhị

đệ nhị
adj

second

đệ tam
adj

(in Sino-Vietnamese words) third

đệ tứ
adj

fourth

đệ tử
noun

(archaic or Chinese fiction, especially martial arts) one's disciple
(of a gang leader) an underling

đệm
noun

mattress; cushion
buffer

verb

to place (under)
to accompany

địt
verb

(Central Vietnam, Southern Vietnam, informal) to fart
(Northern Vietnam, vulgar, colloquial) to fuck

intj

(Northern Vietnam, vulgar, colloquial) Shit!; Fuck!

疊
character

chữ Hán form of điệp (“fold in layers”).

移
character

chữ Hán form of di (“to change place; to move”).
Nôm form of dời (“to move; to relocate”).
Nôm form of đưa (“to give, to hand over”).