A Fortiori

From Latin, "with even stronger reason." It applies to situations in which if one thing is true then it can be inferred that a second thing is even more certainly true. For example, if someone is too young to drive, then his younger brother certainly is too young.

A Posteriori

From Latin, applies to a determination derived from or based on inductive reasoning or empirical evidence. Involves the flow of reasoning from facts to general principals or general causes to effects (as opposed to a priori)

A Priori

From Latin, an assumption based on theory not experiment. For example, an a priori assumption would be that the sun will come up tomorrow. (as opposed to a posteriori)

Ab Initio

From Latin, "from the start". For example, "The contract was void ab initio."

Abandonment

The act of intentionally and permanently giving something away as referred to a child or wife, 2.) relinquishment as referred to a right or estate 3.) careless demonstration of freedom (reckless abandonment)

Abatement

(1) in terms of an amount, the taking away, reduction, or allowed discount (2) in a situation, the suppression or removal of symptoms. For example, "the abatement of pollution."

Abduction

The criminal taking of a person by persuasion, by fraud, or by open force of violence.

Abet

To aid, encourage, support, or approve of something. In law, it is usually a crime that is being carried out.

Abeyance

Temporary inactivity, cessation, or suspension. In law, it is a state or condition of real property in which the title is not as of yet vested in a known title holder.

Able-bodied

Having a strong, healthy body. In law, it is often used to describe a person who is capable of earning a living and, therefore, able to pay alimony or child support.