An Etymological Dictionary of Astronomy and Astrophysics

1. To transform ideas into words; utter or state.
   

2. Math: To → transform into equivalent → terms. For example by → expanding or → factorizing an → expression. See also → suppress, → impress.

Etymology (EN): M.E. expressen, O.Fr. espresser “to press, squeeze out; speak one’s mind,” M.L. expressare, frequentative of exprimere “represent, describe,” literally “to press out,” from → ex- “out” + pressare “to press, push,” from L. premere “to press, hold fast, cover, compress.”

Etymology (PE): Zohâvidan, from zo- variant of os- “out,” → ex-, + hâv, from Av. hau- “to press, squeeze out;”
cf. Mid.Pers. hunîdan “to express, extract (juice),” hâwan “mortar;” akin to Skt. sav- “to press, press out;” O.H.G. sou, O.E. sēaw “juice;” + -idan infinitive suffix.