Rule 15.

Effect of r upon vowels.

[~er] [~ir] [~or] [~ur]
her bird work urn
fern sir word turn
term stir worm hurt
herd girl world purr
jerk first worst burn
ever chirp worth churn
serve whirl worse burst
perch thirst worship church
kernel fir worthy curve
verse firm worry curb
verb third fur
germ birth blur
herb birch curd
stern thirty curl



OTHER EQUIVALENTS

a==e [(a]==[(e]

they eight care heir
obey weight bare their
prey freight fare there