In obsolete|lang=en terms the difference between bailment and mortgage

is that bailment is (obsolete) bail while mortgage is (obsolete) state of being pledged.

In legal|lang=en terms the difference between bailment and mortgage

is that bailment is (legal) the handing over of control over, or possession of, personal property by one person, the bailor, to another, the bailee, for a specific purpose upon which the parties have agreed while mortgage is (legal) to borrow against a property, to obtain a loan for another purpose by giving away the right of seizure to the lender over a fixed property such as a house or piece of land; to pledge a property in order to get a loan.

As nouns the difference between bailment and mortgage

is that bailment is (obsolete) bail while mortgage is (legal) a special form of secured loan where the purpose of the loan must be specified to the lender, to purchase assets that must be fixed (not movable) property such as a house or piece of farm land the assets are registered as the legal property of the borrower but the lender can seize them and dispose of them if they are not satisfied with the manner in which the repayment of the loan is conducted by the borrower once the loan is fully repaid, the lender loses this right of seizure and the assets are then deemed to be unencumbered.

As a verb mortgage is

(legal) to borrow against a property, to obtain a loan for another purpose by giving away the right of seizure to the lender over a fixed property such as a house or piece of land; to pledge a property in order to get a loan.