err-, errat- +

1. Irregular, uncertain or without organization in movement or behavior.
2. Not predictable, regular, or consistent; especially, in being likely to depart from expected standards at any time.
3. Often changing direction and not following any definite course.
4. Having no fixed or regular course; wandering.
5. Lacking consistency, regularity, or uniformity; such as, an erratic heart beat.
6. Variable or unpredictable; such as, the course of an illness or the site of pain.
7. A description of a rock or boulder that was carried from its source by ice and deposited when the ice melted.

A mistake or error in printing or writing; especially, one noted on a list that is included with a printed book.

1. Containing or derived from error; mistaken; such as, erroneous conclusions.
2. Incorrect, based on an incorrect assumption, or containing something that is incorrect.
3. Straying from what is moral, decent, proper, etc.

1. In a mistaken manner.
2. Having made a mistake; being in error.

1. An act, assertion, or belief that unintentionally deviates from what is correct, right, or true.
2. The condition of having incorrect or false knowledge.
3. The act or an instance of deviating from an accepted code of behavior.
4. Something unintentionally done wrong; for example, as a result of poor judgment or lack of care.
5. A belief or opinion that is contrary to fact or to established doctrine.
6. The state of holding incorrect beliefs or opinions, or the fact of acting wrongly or misguidedly caused by human error.
7. The state or fact of being a mistake, or of being inappropriate or unacceptable.
8. In baseball, a fielding misplay, called when the official scorer judges that a play should have either led to an out or prevented a runner from advancing.
9. The failure of a computer program, subroutine, or system to produce an anticipated result.
10. A variation between the true value of a mathematical quantity and a calculated or measured value.
11. Etymology: from Old French errur, from Latin errorem, "a wandering, straying, mistake"; from errare, "to wander".

Free from error.

1. Free from error; infallible.
2. Containing no errors.
3. Incapable of making a mistake.

Indefiniteness or an error in a measurement process that varies unsystematically or unpredictably from measurement to measurement; its magnitude may be quantifiable by statistical methods.

1. Unfailingly accurate or correct.
2. Committing no mistakes; consistently accurate.