There are 592 words ending in "ial" in the Scrabble dictionary. Here are 150 of the more common ones:
actuarial
adverbial
adversarial
aerial
alluvial
ambassadorial
antisocial
arterial
artificial
axial
bacterial
baronial
beneficial
bestial
bicentennial
biennial
binomial
biracial
bronchial
burial
celestial
centennial
ceremonial
circumstantial
colloquial
colonial
commercial
confidential
congenial
connubial
consequential
conspiratorial
controversial
convivial
cordial
cranial
credential
crucial
custodial
deferential
denial
dial
dictatorial
differential
editorial
entrepreneurial
equatorial
equinoctial
especial
essential
existential
exponential
extraterrestrial
facial
familial
filial
financial
genial
glacial
gladiatorial
gubernatorial
immaterial
immemorial
impartial
imperial
inconsequential
industrial
inertial
inessential
inferential
influential
infomercial
initial
insubstantial
interracial
jovial
judicial
labial
magisterial
malarial
managerial
manorial
marsupial
martial
material
matrimonial
medial
memorial
menial
mercurial
millennial
ministerial
mistrial
multiracial
nonessential
nuptial
official
palatial
parochial
partial
participial
patrimonial
penitential
perennial
phial
pictorial
polynomial
potential
preferential
prejudicial
presidential
primordial
professorial
proverbial
providential
provincial
prudential
purgatorial
quintessential
racial
radial
remedial
residential
retrial
reverential
sacrificial
sartorial
secretarial
senatorial
sequential
serial
social
spatial
special
substantial
sundial
superficial
tangential
terrestrial
territorial
testimonial
tonsorial
torrential
trial
triennial
trivial
tutorial
unofficial
unsubstantial
venial
vestigial
vial
commercial
Special.
Dial.
Trial.
Perennial.
Initial.
Partial.
Impartial.
Cordial.
Bestial.
Denial.
Partial, facial, superficial, presidential, national,...
the prefix for presidential is pre and the suffix is ial
ial
ial
Remove the e, and add -ial.
In short it means 'of' or 'coming from'.