We often embed items from one space into another space, e.g. embedding plaintext items from $\{0, 1\}^m$ into some ring $R_q/\langle x^N + 1 \rangle$ for RingLWE.
What is the inverse of this action called?
(Feel free to move this question to Math.SE or other related. Though I am specifically interested in the opposite of embed in the context of math and crypto, rather than the general English language.)