1.
to put in, to insert
To place something inside a container, space, or location. The opposite of 出す (to take out).
2.
to include, to add
To include someone or something as part of a group or mixture.
TRANSITIVITY: 他動詞 (transitive). Pair: 入る (intransitive, to enter). Pattern: XをYに入れる (put X into Y).
ASPECT: ている indicates resulting state. 入れている = 'have put in (and it's still in there)' or 'is putting in.'
COMMON PATTERNS:
Opposite: 出す (to take out).