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to enter; to go in; to get in; to come in
to set (of the sun or moon); to sink; to go down
to attain (nirvana, enlightenment, etc.); to achieve; to reach (e.g. a climax)
to do fully; to do intently; to do sincerely; to do deeply; to feel keenly
to (reach a state) completely
「入る」 has another reading with different meanings.
日が山に入って辺りが暗くなった。
The sun went behind the mountain and the surroundings grew dark.
太陽がもう入るね。
The sun is setting already, isn't it?
彼は悟りに入った。
He attained enlightenment.