enter, insert
入 centers on the idea of going or putting something into a space: entering a place or inserting an object.
to enter; to come in; to go in; to get in; to arrive
to enter; to go in; to get in; to come in
to put in; to let in; to take in; to bring in; to insert; to install (e.g. software); to set (a jewel, etc.); to ink in (e.g. tattoo)
entering; entrance; entry
purchase; buying
introduction; bringing in; installation; setting up; importation
income; earnings; revenue; proceeds; takings; receipts
receiving; acceptance; reception; admission
acquisition; obtaining; procurement; getting (hold of)
favorite; favourite; pet (e.g. teacher's pet)
input; (data) entry; typing
admission (to a school or university); entrance; enrolment; enrollment; matriculation
import; importation; introduction
invasion; incursion; raid; aggression; intrusion; trespass; penetration; hacking
insertion; interposition; interpolation; infixing; (sexual) penetration
hospitalization; hospitalisation
joining (a club, organization, etc.); becoming a member; entry; admission; subscription; affiliation; signing (e.g. a treaty); taking out (insurance)
entrance; entering; admission; admittance
throwing in; inserting; depositing (e.g. a ballot)
rushing into; breaking into; storming
arrival of goods; goods received
joining a company; getting a job with a company; starting work at a company
to accept; to receive; to agree
entrance; entry; gate; approach; mouth
入 is a pictograph of something entering or being inserted, with the strokes suggesting a pointed object going into an opening.
The two strokes look like an arrowhead or a wedge being pushed into a gap. Picture the tip entering a narrow space.
For ニュウ, imagine a new employee entering the office for the first time: new -> ニュウ, and they step inside.