đêm

Etymology
From, probably from. Cognate with 🇨🇬, 🇨🇬 [Cuối Chăm] teːm¹. Compare 🇨🇬, 🇨🇬, 🇨🇬 [Cuang] psɨəm, 🇨🇬 [Lang] sɔm¹.

The Vietnamese words for "day" and "night" and their cognates have the same distribution within Vietic: reflexes of and  are only attested in Thổ, Pong and Viet-Muong, i.e. the "innovative Vietic" group, lacking cognates in the generally more conservative languages. Unlike the case of (> ), the existence of presyllable (if it existed) in Vietic can not be straightforwardly recovered: the tone of the word is consistently A1 in all languages, indicating what was most likely a monosyllabic root with voiceless onset (what the root is currently reconstructed as). The mismatch of vowels (Vietic showing front vowel, while the rest showing central or back vowels) is probably the biggest hindrance to connect đêm to other AA words. The cognacy between Vietnamese đêm and the other AA words, therefore, might be questionable.

Non-final *t in the non-Northern branches sometimes corresponds to a fricative, an affricate or a palatal stop in Northern branches, cf. and in Proto-Khmuic, whose Proto-Vietic cognates are  (> Vietnamese ) and  (> ) respectively.

Noun

 * 1) night, especially late night after 9 PM, including the wee hours of the morning; the overnight hours; compare