As nouns the difference between thier and tier
is that thier is while tier is animal.
thier
English
Pronoun
(head)
tier
English
Etymology 1
(tie)
Noun
(
en noun)
One who ties (knots, etc).
Something that ties.
Etymology 2
From (etyl), (etyl) .
Noun
(
en noun)
A layer or rank, especially of seats or a wedding cake.
Verb
(
en verb)
To arrange in layers.
To cascade in an overlapping sequence.