Allow for

to give permission to or for; permit:
to allow a student to be absent; no swimming allowed.
to let have; give as one’s share; grant as one’s right:
to allow a person $100 for expenses.
to permit by neglect, oversight, or the like:
to allow a door to remain open.
to admit; acknowledge; concede:
to allow a claim.
to take into consideration, as by adding or subtracting; set apart:
to allow an hour for changing trains.
older use. to say; think.
archaic. to approve; sanction.
to permit something to happen or to exist; admit (often followed by of):
to spend more than one’s budget allows; a premise that allows of only one conclusion.
allow for, to make concession or provision for:
to allow for breakage.
verb
(transitive) to permit (to do something); let
(transitive) to set aside: five hours were allowed to do the job
(transitive) to let enter or stay: they don’t allow dogs
(transitive) to acknowledge or concede (a point, claim, etc)
(transitive) to let have; grant: he was allowed few visitors
(intransitive) foll by for. to take into account: allow for delays
(intransitive) often foll by of. to permit; admit: a question that allows of only one reply
(transitive; may take a clause as object) (us, dialect) to -ssert; maintain
(transitive) (archaic) to approve; accept
v.

early 14c., allouen, “to commend, praise; approve of, be pleased with; appreciate the value of;” also, “take into account or give credit for,” also, in law and philosophy, “recognize, admit as valid” (a privilege, an excuse, a statement, etc.). from late 14c. as “sanction or permit; condone;” in business use from early 15c.

the middle english word is from anglo-french alouer, old french aloer, alloiier (13c.) “allot, apportion, bestow, -ssign,” from latin allocare (see allocate). this word in old french was confused and ultimately merged with aloer; alloer “to praise, commend,” from latin allaudare, adlaudare, compound of ad- “to” (see ad-) + laudare “to praise” (see laud). from the first word came the sense preserved in allowance as “money granted;” from the second came its meaning “permission based on approval.”

between the two primary significations there naturally arose a variety of uses blending them in the general idea of -ssign with approval, grant, concede a thing claimed or urged, admit a thing offered, permit, etc., etc. [oed].

related: allowed; allowing.

leave room for, permit, as in we have enough chairs to allow for forty extra guests, or our denomination allows for a large variety of beliefs. [ early 1700s ]
also see: make allowance