confused

[lav]

https://englishplus.com/grammar/00000167.htm

can someone help me make correct sentences using

• 1.an only child (o sound) ... i think it should be the only child
  2.a once-happy lover (w sound)./.. should it be once a happy lover ?

[Karen]

"an only child" is an idiomatic expression meaning a child with no brothers or sisters, as in "He was an only child, and spent more time around adults than around other children."

"a once-happy lover" means a lover who was happy at some time in the past.

[lav]

thanks Karen for your response
Talking of two choices ...
a) He is an Honest Man
b) He is a Honest Man

If i am running out of time, in a hurry , Its easy to support choice B. I am confused this USED tobe the most simple rule using a or an , now i cam getting confused

More examples , articles or discussion will be appreciated

[griscomtestprep]

We only use 'an' when the next sound is a vowel sound. 'Honest' begins with an 'ah' sound, so takes 'an' before it. 'Only' begins with an 'oh' sound, so also takes 'an.'

'Once,' on the other hand begins, with a 'wuh' sound, and so doesn't need 'an.'