What is Aid?

Legal Definition
In international relations, aid (also known as international aid, overseas aid, foreign aid or foreign assistance) is – from the perspective of governments – a voluntary transfer of resources from one country to another.

Aid may serve one or more functions: it may be given as a signal of diplomatic approval, or to strengthen a military ally, to reward a government for behaviour desired by the donor, to extend the donor's cultural influence, to provide infrastructure needed by the donor for resource extraction from the recipient country, or to gain other kinds of commercial access. Humanitarian and altruistic purposes are at least partly responsible for the giving of aid.

Aid may be given by individuals, private organizations, or governments. Standards delimiting exactly the types of transfers considered "aid" vary from country to country. For example, the United States government discontinued the reporting of military aid as part of its foreign aid figures in 1958. The most widely used measure of aid is "Official Development Assistance" (ODA).
-- Wikipedia
Legal Definition
Engl. law. Formerly they were certain sums of money granted by the tenant to his lord in times of difficulty and distress, but, as usual in such cases, what was received as a gratuity by the rich and powerful from the weak and poor, was soon claimed as a matter of right; and aids became a species of tax to be paid by the tenant to his lord, in these cases: 1. To ransom the lord's person, when taken priisoner; 2. To make the lord's eldest son a knight; – 3. To marry the lord's eldest daughter, by giving her a suitable portion. The first of these remained uncertain; the other two were fixed by act of parliament at twenty shillings each being the supposed twentieth part of a knight's fee, 2 Bl. Com. 64.
-- Bouviers Law Dictionary
Legal Definition
v. To support, help or assist. This word must be distinguished from Its synonym "encourage," the differenco being that the former connotes active support and assistance, while the latter does not; and also from "abet," which last word imports necessary criminality in the act furthered, while "aid," standing alone, does not. See Abet.
-- Black's Law Dictionary
Legal Definition
In feudal law, originally mere benevolences granted by a tenant to his lord, in times of distress; but at length the lords claimed them as of right. They were principally three:

(1) To ransom the lord's person, if token prisoner;

(2) to make the lord's eldest son and heir apparent a knight;

(3) to give a suitable portion to the lord's eldest daughter on her marriage. Abolished by 12 Car. II. c. 24. Also, extraordinary grants to the crown by the house of commons, and which were the origin of the modern system of taxation. 2 Bl. Comm. 63, 64. See Reasonable aid.
-- Black's Law Dictionary
Legal Definition
Services or payments to the lord by a tenant in chivalry on certain occasions and as aid pur faire Teigne, etc.
-- Ballentine's Law Dictionary