Same /i/ sound: only the spelling changes. After the linking u and after qu, write y (tuy, quý). In some words i and y are free variants: kỳ or kì, lý or lí. Not to be confused with ai / ay, where the length of the a changes.
tuy · quý · kỳ · kì
o or u for the linking sound?
The small linking sound /w/ is written o before a, ă, e (hoa, hoặc, hoe) and u before the other vowels (huế, tuy). After q it is always the u of qu, written once: quan sounds like toán, quân like tuần.
hoa · hoặc · khoẻ · huế · tuyết · quan · quân
nh / ch at the end
The finals NH and CH only come after a, ê and i (anh, ếch, ích). After ê and i, always NH / CH, never ng / c (bệnh, ích). After a, both exist and make different words (anh / ang, ách / ác). In the South, -nh sounds like -n (anh = /an/).
anh · bánh · ích · bệnh · sạch
Quick answers
How do you pronounce Huỳnh?
Block by block: i → nh → inh → uynh → h → huynh → huyền → huỳnh. Tone: huyền (grave accent · low falling). Read each block aloud, then compare with the recording, in a Southern or a Northern voice.
What tone is Huỳnh?
huyền (grave accent · low falling)
Is Huỳnh said differently in the South and the North?
South · Sài Gòn: uynh = uyn. North · Hà Nội: said as written.
What does “huynh” mean without the marks?
Without the marks, huynh can be several words: huynh (elder brother). The marks decide which one.