to explore or investigate deeply
explorer ou enquêter en profondeur (explorer ou enquêter en profondeur)
"The scientist decided to delve in to the mysteries of the deep sea."
"Le scientifique a décidé de plonger dans les mystères des profondeurs marines." (Le scientifique a décidé de **delve in** dans les mystères des profondeurs marines.)
to contact an organization in writing regarding something
to remove unwanted elements or inefficiencies
to gradually develop into a more mature or confident person
to increase a country's foreign currency holdings
to go to the place where someone is leaving from to say good...
to write something again exactly as it is