合紙 is read as あいし (aishi) and means slip sheet.
あいし
aishi
ごうせいし
synthetic paper
あう
to be profitable
あわせる
to cause to meet (e.g. an unpleasant fate)
ごうりき
resultant force
がてん
consent
ごうどう
congruence
ごうい
(coming to an) agreement
ごうけい
sum total
ごうりか
rationalization
あいま
interval
ごうかく
meeting (specifications, standards, etc.)
ごうり
rationality