What is Admission?

Legal Definition
An admission in the law of evidence is a prior statement by an adverse party which can be admitted into evidence over a hearsay objection. In general, admissions are admissible in criminal and civil cases.

At common law, admissions were admissible. A statement could only be excluded by a showing of involuntariness, unfairness, or that the circumstances under which the statement was obtained was improper or illegal.

In the United States, "Admission by a party-opponent" is explicitly excepted from hearsay under the Federal Rules of Evidence. Rule 801(d)(2). Among several types of admissions, the rule notes that an admission can be the "party's own statement" or a statement in which the "party has manifested an adoption or belief in its truth."

Under both common law and the Federal Rules of Evidence, an admission becomes legally invalid after nine years from the date of the initial admission.
-- Wikipedia
Legal Definition
1) A person's, in particular a party's, statement acknowledging that a certain fact is true or silence after another party's assertion of a fact that, if false, would typically elicit a denial. 2) Admission by a party-opponent: an out-of-court statement by a party that is against the party's interest and that is admissible against the party, because admissions by party-opponents are not considered hearsay.
Illustrative caselaw
See, e.g. Rawlings v. Kentucky, 448 U.S. 98 (1980).
See also
Legal Definition
In corporations or companies. The act of the corporation or company by which an individual acquires the rights of a member of such corporation or company.

2. In trading and joint stock corporations no vote of admission is requisite; for any person who owns stock therein, either by original subscription or by conveyance, is in general entitled to, and cannot be refused, the rights and privileges of a member. 3 Mass. R. 364; Doug. 524; 1 Man. & Ry. 529.

3. All that can be required of the person demanding a transfer on the books, is to prove to the corporation his right to the property. See 8 Pick. 90.

4. In a Mutual Insurance Company, it has been held, that a person may become a member by insuring his property, paying the premium and deposit-money, and rendering himself liable to be assessed according to the rules of the corporation. 2 Mass. R. 315.
-- Bouviers Law Dictionary
Legal Definition
In evidence. A voluntary acknowledgment, confession or concession of the existence of a fact or the truth of an allegation made by a party to the suit. Roosevelt v. Smith, 17 Misc. Rep. 323, 40 N. Y. Supp. 381.

In pleading. The concession or acknowledgment by one party of the truth of some matter alleged by the opposite party, made in a pleading, the effect of which is to narrow the area of facts or allegations requiring to be proved by evidence. Connecticut Hospital v. Brookfield, 69 Conn. 1, 36 Atl. 1017.

In practice. The formal act of a court, by which attorneys or counsellors are recognized as officers of the court and are licensed to practice before it.

In corporations. The act of a corporation or company by which an individual acquires the rights of a member of such corporation or company.

In English ecclesiastical law. The act of the bishop, who, on approval of the clerk presented by the patron, after examination, declares him fit to serve the cure of tne church to which he is presented, by the words "admitto te habilem," I admit thee able. Co. Litt. 344a; 4 Coke, 79; 1 Crabb, Real Prop. p. 138, ยง 123.

Synonyms. The term "admission" is usually applied to civil transactions and to these matters of fact in criminal cases which do not involve criminal intent, while the term "confession" is generally restricted to acknowledgments of guilt. People v. Velarde, 59 Cal. 457 ; Colburn v. Groton. 66 N. H. 151, 28 Atl. 95, 22 L. R. A. 763; State v. Porter, 32 Or. 135, 49 Pac. 964.
-- Black's Law Dictionary