estimation (n.) Look up estimation at Dictionary.com
late 14c., "action of appraising; manner of judging; opinion," from Old French estimacion "evaluation, value; calculation, planning," from Latin aestimationem (nominative aestimatio) "a valuation," from past participle stem of aestimare "to value" (see esteem (v.)). Meaning "appreciation" is from 1520s. That of "process of forming an approximate notion" is from c.1400.