An Etymological Dictionary of Astronomy and Astrophysics

1. The state or quality of being → accurate.
   

2. The degree of nearness of a measured value to the standard or known value of the quantity, not to be confounded with → precision.

For example, a refrigerator holds a constant temperature of 5.0 °C. A thermometer is used seven times to read the temperature, with the following results: 6.4, 5.1, 6.3, 4.5, 5.3, 6.1, and 4.1. This distribution does not well match the actual temperature, therefore it lacks accuracy, and shows no tendency toward a particular value; it lacks precision, as well.

If the measured temperatures are 4.8, 5.3, 5.1, 5.0, 4.6, 5.2, and 5.0, the mean value is accurate, because it comes close to the actual temperature, but the distribution shows no clear tendency toward a particular value (lack of precision).

Now suppose that the measured temperatures are 6.2, 6.3, 6.1, 6.0, 6.1, 6.3, and 6.2. In this case every measurement is well off from the actual temperature (low accuracy), but the distribution does show a tendency toward a particular value (high precision).

Finally, if the measured temperatures are 5.0, 5.0, 4.8, 5.1, 5.0, 4.9, and 5.0, the distribution is very near the actual temperature each time (high accuracy), and does show a tendency toward a particular value (high precision).

Accuracy is often given to n → significant digits or n → decimal places.
For example e = 2.71828 … = 2.718 is rounded to two four significant figures or three decimal places. → accurate to n significant figures, → accurate to n decimal places.

Etymology (EN): From L. accuratus “prepared with care, exact,” p.p. of accurare “take care of,” from ad- “to” + curare “take care of.”

Etymology (PE): Rašmandi, from rašmand, from raš + adjective forming suffix -mand. Raš, from Av. root raz- “to right, correct, arrange;”
compare with Skt. raj “to reign, rule, direct,” Gk. oregein “to strech out,” L. rego “to direct, lead;” PIE *reg- “to move in a straight line.” Similarly, Av. râšta-, rašta- “straight,” Skt. rju “straight, right, upright,” Gk. orektos “elongated,” L. rectus “straight,” Ger. recht, E. right. In Mod.Pers. there are several derivatives:
râst, râšt (as in afrâšt(an)) “right; true,” rasté, rešté, raj, raž, râh, ris, râdé, radé, Lori rezg “row,” etc.