This is the 10024th most frequent Japanese word.
込
"込" means "to go/move into," "to be included," or "to be filled."
The word '込' is part of '取り込む', meaning 'to engage in' or 'to be absorbed in'.
彼は仕事に熱心に取り込んでいます。
He is enthusiastically engaged in his work.
Here '込' appears in '込む', signifying fullness or being crowded.
列車が駅に込んでいましたので、乗るのが大変でした。
The train was crowded at the station, so boarding was difficult.
In this sentence, '込' is used in '込める', which means 'to put effort into' or 'to involve deeply'.