Vowel harmony & dual suffixes

Vowel harmony chooses the vowel inside a consonant-attaching suffix. The stem itself never changes.

The dual-suffix rule

Every suffix has two shapes: consonant-initial after a vowel-final base, vowel-initial after a consonant-final base.

vowel-final base → consonant-initial suffix (e.g. tomo + n → tomon)
consonant-final base → vowel-initial suffix (e.g. hop + un → hopun, kiv + in → kivin)
back vowels: a o u → u-series
front vowels: e i → i-series

Look at the current base (stem + already attached suffixes).
If it ends in a vowel → use the consonant-initial suffix shape.
If it ends in a consonant → use the vowel-initial shape.
For vowel-initial shapes, read the last vowel of the original stem: a/o/u → back (u-series), e/i → front (i-series).
Never change letters inside the stem.

Suffix pairs

Role	Shapes
Plural	-n / -un\|-in
Accusative	-t / -ut\|-it
Inessive	-k / -uk\|-ik
Past	-d / -ud\|-id
Future	-b / -ub\|-ib

Examples

tomo + n → tomon

house + PL (V-final → -n)

kiv + in → kivin

bicycle + PL (C-final front → -in)

hop + un → hopun

tent + PL (C-final back → -un)

tomo + k → tomok

house + INE (V-final → -k)

hop + uk → hopuk

tent + INE (C-final back → -uk)

kere + k → kerek

garden + INE (V-final → -k; stem stays kere-)