This is the 3458th most frequent Japanese word.
甲斐
"甲斐" means "worth," "value," or "reward (of effort)."
Here, '甲斐' is used to express that the effort (努力) yielded meaningful results, showing its application as a term indicating worth or value.
努力の甲斐があった。
The effort was worthwhile.
In this sentence, '甲斐' is again used to denote that the hard work (必死に働いた) resulted in something worthwhile or significant.
必死に働いた甲斐があった。
The desperate work was worth it.
The word '甲斐' in this context highlights the value and positive outcome of someone's assistance (援助), underscoring its use in describing the fruitfulness of an action or effort.