ripen
verb uk/ˈraɪ.pən/ us/ˈraɪ.pən/
[ I or T ]（使）成熟
to (cause to) become ripe
The summer sunshine ripened the melons. 在夏日阳光的照射下，瓜熟了。
These melons are ripening nicely. 这些瓜马上就熟透了。
[ I ]时机成熟；条件成熟
to develop to a suitable condition for something to happen
My plans are ripening - now all I need is official approval. 我的计划就要瓜熟蒂落了——现在就差官方的批准了。