What is Conviction?

Legal Definition
In law, a conviction is the verdict that results when a court of law finds a defendant guilty of a crime. The opposite of a conviction is an acquittal (i.e. "not guilty"). In Scotland and in the Netherlands, there can also be a verdict of "not proven", which counts as an acquittal. There are also cases where the court orders that a defendant not be convicted, despite being found guilty; in England, Wales and Canada the mechanism for this is a discharge.

For a host of reasons, the criminal justice system is not perfect, and sometimes guilty defendants are acquitted, while innocent people are convicted. Appeal mechanisms and post conviction relief procedures may mitigate the effects of a conviction to some extent. An error which results in the conviction of an innocent person is known as a miscarriage of justice.

After a defendant is convicted, the court determines the appropriate sentence as a punishment. Furthermore, the conviction may lead to results beyond the terms of the sentence itself. Such ramifications are known as the collateral consequences of criminal charges.

A minor conviction is a warning conviction, and it does not affect the defendant but does serve as a warning.

A history of convictions are called antecedents, known colloquially as "previous" in the United Kingdom, and "priors" in the United States and Australia. The history of convictions also shows that a minor law conviction can be prosecuted as any individuals punishment.
-- Wikipedia
Legal Definition
Practice. A condemnation. In its most extensive sense this word signifies the giving judgment against a defendant, whether criminal or civil. In a more limited sense, it means, the judgment given against the criminal. And in its most restricted sense it is a record of the summary proceedings upon any penal statute before one or more justices of the peace, or other persons duly authorized, in a case where the offender has been convicted and sentenced: this last is usually termed a summary conviction.

2. As summary. convictions have been introduced in derogation of the common law, and operate to the exclusion of trial by jury, the courts have required that the strict letter of the statute should be observed 1 Burr. Rep. 613 and that the magistrates should have been guided by rules similar to those adopted by the common law, in criminal prosecution, and founded in natural justice; unless when the statute dispenses with the form of stating them.

3. The general rules in relation to convictions are, first, it must be under the hand and seal of the magistrate before whom it is taken; secondly, it must be in the present tense, but this, perhaps, ought to extend only to the judgment; thirdly, it must be certain; fourthly, although it is well to lay the offence to be contra pacem, this is not indispensable; fifthly, a conviction cannot be good in part and bad in part.

4. A conviction usually consists of six parts; first, the information; which should contain, 1. The day when it was taken. 2. The place where it was taken. 3. The name of the informer. 4. The name and style of the justice or justices to whom it was given. 5. The name of the offender. 6. The time of committing the offence. 7. The place where the offence was committed. 8. An exact decription of the offence.

5. Secondly, the summons.

6. Thirdly, the appearance or non-appearance of the defendant.

7. Fourthly, his defence or confessions.

8. Fifthly, the evidence. Dougl. 469; 2 Burr. 1163; 4 Burr. 2064.

9. Sixthly, the judgment or adjudication, which should state, 1. That the defendant is convicted. 2. The forfeiture or penalty. Vide Bosc. on Conviction; Espinasse on Penal Actions; 4 Dall. 266; 3 Yeates, 475; 1 Yeates, 471. As to the effect of a conviction as evidence in a civil case, see 1 Phil. Ev. 259; 8 Bouv. Inst. 3183.
-- Bouviers Law Dictionary
Legal Definition
In practice. In a general sense, the result of a criminal trial which ends in a Judgment or sentence that the prisoner is guilty as charged. Finding a person guilty by verdict of a Jury. 1 Bish. Crim. Law, ยง 223. A record of the summary proceedings upon any penal statute before one or more justices of the peace or other persons duly authorized, in a case where the offender has been convicted and sentenced. Holthouse. In ordinary phrase, the meaning of the word "conviction" is the finding by the jury of a verdict that the aceused is guilty. But, in legal parlance, it often denotes the final Judgment of the court. Blaufus v. People, 69 N. Y. 109, 25 Am. Rep. 148. The ordinary legal meaning of "conviction." when used to designate a particular stage of a criminal prosecution triable by a jury, is the confession of the accused in open court, or the verdict returned against him by the jury, which ascertains and publishes the fact of his guilt; while "judgment" or "sentence" is the appropriate word to denote the action of the court before which the trial is had, declaring the consequences to the convict of the fact thus ascertained. A pardon granted after verdict of guilty, but before sentence, and pending a hearing upon exceptions taken by the aceused during the trial, is granted after conviction; within the meaning of a constitutional restriction upon granting pardon before conviction. When, indeed, the word "conviction" is used to describe the effect of the guilt of the accused as judicially proved in one case, when pleaded or given in evidence in another, it is sometimes used in a more comprehensive sense, including the judgment of the court upon the verdict or confession of guilt; as, for instance, in speaking of the plea of autrefois convict, or of the effect of guilt, judicially ascertained, as a disqualification of the convict. Co.m. v. Lockwood, 109 Mass. 323, 12 Am. Rep. 699.
See also
-- Black's Law Dictionary
Legal Definition
Finding guilty one accused of crime. See 48 La. Ann. 109, 35 L. R. A. 701, 18 South. 943.
-- Ballentine's Law Dictionary