What is Apprenticeship?

Legal Definition
An apprenticeship is a system of training a new generation of practitioners of a trade or profession with on-the-job training and often some accompanying study (classroom work and reading). Apprenticeship also enables practitioners to gain a license to practice in a regulated profession. Most of their training is done while working for an employer who helps the apprentices learn their trade or profession, in exchange for their continued labor for an agreed period after they have achieved measurable competencies. Apprenticeships typically last 3 to 6 years. People who successfully complete an apprenticeship reach the "journeyman" or professional certification level of competence.

Although the formal boundaries and terminology of the apprentice/journeyman/master system often do not extend outside of guilds and trade unions, the concept of on-the-job training leading to competence over a period of years is found in any field of skilled labor.

In early modern usage, the clipped form prentice was common.
-- Wikipedia
Legal Definition
Contracts. A contract entered into between a person who understands some art, trade or business, and called the master, and another person commonly a minor, during his or her minority, who is called the apprentice, with the consent of his or her parent or next friend by which the former undertakes to teach such minor his art, trade or business, and to fulfil such other covenants as may be agreed upon; and the latter agrees to serve the master during a definite period of time, in such art, trade or business. In a common indenture of apprenticeship, the father is bound for the performance of the covenants by the son. Daug. 500.

2. The term during which the apprentice is to serve is also called his apprenticeship. Pardessus, )Dr. Com. n. 34.

3. This contract is generally entered into by indenture or deed, and is to continue no longer than the minority of the apprentice. The English statute law as to binding out minors as apprentices to learn some useful art,. trade or business, has been generally adopted in the United States, with some variations which cannot, be noticed here. 2 Kent, Com. 212.

4. The principal duties of the parties are as follows: 1st, Duties of the master. He is bound to instruct the apprentice by teaching him, bona fide, the knowledge of the art of which he has undertaken to teach him the elements. He ought to, watch over the conduct of the apprentice, giving him prudent advice and showing him a good example, and fulfilling towards him the duties of a father, as in his character of master, he stands in loco parentis. He is also required to fulfil all the covenants he has entered into by the indenture. He must not abuse his authority, either by bad treatment, or by employing his apprentice in menial employments, wholly unconnected with the business he has to learn. He cannot dismiss his apprentice except by application to a competent tribunal, upon whose, decree the indenture may be cancelled. But an infant apprentice is not capable in law of consenting to his own discharge. 1 Burr. 501. Nor can the justices, according to some authorities, order money to be returned on the discharge of an apprentice. Strange, 69 Contra, Salk. 67, 68, 490; 11 Mod. 110 12 Mod. 498, 553. After the apprenticeship is at an end, he cannot retain the apprentice on the ground that he has not fulfilled his contract, unless specially authorized by statute.

5. – 2d. Duties of the apprentice. An apprentice is bound to obey his master in all his lawful commands, take care of his property, and promote his interest, endeavor to learn his trade or business, and perform all the covenants in his indenture not contrary to law. He must not leave his master's service during the term of the apprenticeship. The apprentice is entitled to payment for extraordinary services, when promised by the master; 1 Penn. Law Jour. 368. See 1 Whart. 113; and even when no express promise has been made, under peculiar circumstances. 2 Cranch, 240, 270; 3 Rob. Ad. Rep. 237; but see 1 Whart, 113. See generally, 2 Kent, Com. 211-214; Bac. Ab. Master and Servabt; 1 Saund. R. 313, n. 1, 2, 3, and 4; 3 Rawle, R. 307 3 Vin. Ab. 19; 1 Bouv. Inst. n. 396, et seq. The law of France on this subject is strikingly similar to our own. Pardessus, Droit Com. n. 518-522.

6. Apprenticeship is a relation which cannot be assigned at the common law 5 Bin. 428 4 T. R. 373; Doug. 70 3 Keble, 519; 12 Mod. 554; although the apprentice may work with a second master by order and consent of the first, which is a service to the first under the indenture. 4 T. R. 373. But, in Pennsylvania and some other states the assignment of indentures of apprenticeship is authorized by statute. 1 Serg. & R. 249; 3 Serg. & R. 161, 164, 166.
-- Bouviers Law Dictionary
Legal Definition
A contract by which one person, usually a minor, called the "apprentice," is bound to another person, called the "master," to serve him during a prescribed term of ycars in his art, trade or business, in consideration of being instructed by the master in such art or trade, and (commonly) of receiving his support and maintenance from the master during such term. The term during which an apprentice is to serve. The status of an apprentice; the relation subsisting between an apprentice and his master.
-- Black's Law Dictionary