en-1

1.
a prefix occurring originally in loanwords from French and productive in English on this model, forming verbs with the general sense “to cause (a person or thing) to be in” the place, condition, or state named by the stem; more specifically, “to confine in or place on” (enshrine; enthrone; entomb); “to cause to be in” (enslave; entrust; enrich; encourage; endear); “to restrict” in the manner named by the stem, typically with the additional sense “on all sides, completely” (enwind; encircle; enclose; entwine). This prefix is also attached to verbs in order to make them transitive, or to give them a transitive marker if they are already transitive (enkindle; enliven; enshield; enface).
Also, before labial consonants, em-1 .
Compare be-, in-2 .
Origin
Middle English < Old French < Latin in- in-2

en-2

1.
a prefix meaning “within, in,” occurring in loanwords from Greek:
energy; enthusiasm.
Also, before labial consonants, em-2 .
Origin
< Greek (often through L); cognate with in-1, in-2
British Dictionary definitions for en-

en-1

prefix
1.
(from nouns)
  1. put in or on: entomb, enthrone
  2. go on or into: enplane
  3. surround or cover with: enmesh
  4. furnish with: empower
2.
(from adjectives and nouns) cause to be in a certain condition: enable, encourage, enrich, enslave
Word Origin
via Old French from Latin in-in-²

en-2

prefix
1.
in; into; inside: endemic
Word Origin
from Greek (often via Latin); compare in-1, in-²
Word Origin and History for en-

assimilated to -p-, -b-, -m-, -l-, -r-, word-forming element meaning "in, into," from French and Old French en-, from Latin in- "in, into" (see in- (2)).

Also used with native elements to form verbs from nouns and adjectives, "put in or on" (encircle), also "cause to be, make" (endear), and used as an intensive (enclose). Spelling variants in French that were brought over into Middle English account for parallels such as assure/ensure/insure.

assimilated to -p-, -b-, -m-, -l-, -r-, word-forming element meaning "near, at in, on, within," from Greek en "in," cognate with Latin in (see in), and with en- (1).

en- in Medicine

en- 2 or em-
pref.
In; into; within: enzootic.