-ise1

1.
Chiefly British. variant of -ize:
organise.
Usage note
See -ize.

-ise2

1.
a noun suffix, occurring in loanwords from French, indicating quality, condition, or function:
franchise; merchandise.
Compare -ice.
Origin
Middle English < Old French -ise, variant of -ice
British Dictionary definitions for -ise

-ise

suffix
1.
a variant of -ize
-ize

-ize

suffix
1.
to cause to become, resemble, or agree with: legalize
2.
to become; change into: crystallize
3.
to affect in a specified way; subject to: hypnotize
4.
to act according to some practice, principle, policy, etc: economize
Usage note
In Britain and the US -ize is the preferred ending for many verbs, but -ise is equally acceptable in British English. Certain words (chiefly those not formed by adding the suffix to an existing word) are, however, always spelt with -ise in both Britain and the US: advertise, revise
Word Origin
from Old French -iser, from Late Latin -izāre, from Greek -izein
Word Origin and History for -ise

see -ize.