This is the 5558th most frequent Japanese word.
がってん
Understood; agreement; consent.
In this sentence, 'がってん' indicates comprehension or acknowledgement.
がってん承知しました。
Understood completely.
Here, 'がってん' is used to express understanding or agreement.
その説明にがってんがいく。
That explanation makes sense.
In this context, 'がってん' refers to the concept of understanding or agreement.