allow vs allowable

allow is not an adjective while allowable is an adjective.

Word	Noun	Adjective	Verb	Adverb
allow	No	No	Yes	No
allowable	No	Yes	No	No

allow (adjective)	allowable (adjective)
	that may be permitted especially as according to rule
	deserving to be allowed or considered
	deductible according to the tax laws

allow (verb)	allowable (verb)
allow or plan for a certain possibility; concede the truth or validity of something
give or assign a resource to a particular person or cause
consent to, give permission; permit
allow the presence of or allow (an activity) without opposing or prohibiting
let have
grant as a discount or in exchange
make it possible through a specific action or lack of action for something to happen
allow the other (baseball) team to score
make a possibility or provide opportunity for; permit to be attainable or cause to remain
afford possibility