to a great depth psychologically or emotionally
"They felt the loss deeply"
"she loved him intensely"
To a deep extent or degree; very greatly.
"The tragedy deeply affected everyone who attended the ceremony."
In plain English: Deeply means feeling something very strongly, such as being truly sad about a loss.
"She was deeply moved by the touching story."
Usage: Use deeply to intensify adjectives and past participles, such as in the phrase "deeply concerned," rather than modifying verbs directly. It conveys a high degree of emotion or intensity more naturally than synonyms like "very" when describing feelings or reactions.
The word "deeply" comes directly from the Middle English phrase dēoplīċe, which was formed by adding a suffix meaning "-like" or "-wise" to the Old English adjective for depth. It entered English with its current adverbial sense of great intensity, evolving naturally from the root word describing physical depth.