Possibly dumb word puzzle

[kyro]

There is a combination of 4-letters that when found at the end of 5 different words, produce 5 completely different pronounciations (in the typical English language).

what is the 4-letter combination?

Answers in white please.

[fmxda]

did not really try every combo out, but my first instinct was
<font color="white"> S I O N </font>

[His Boy Elroy]

<font color="white">ough</font>

[kyro]

[ QUOTE ]
<font color="white">ough</font>

[/ QUOTE ]

Yep.

[His Boy Elroy]

<font color="white">
rough
trough
bough
through
dough</font>

[fmxda]

ohh, thats what it meant

[metsandfinsfan]

not bad

[DavidC]

Thanks.