deepen

As verbs the difference between expend and deepen

is that expend is (label) to consume, exhaust (some resource) while deepen is to make deep or deeper.

As verbs the difference between subside and deepen

is that subside is to sink or fall to the bottom; to settle, as lees while deepen is to make deep or deeper.

As verbs the difference between deepen and boost

is that deepen is to make deep or deeper while boost is to lift or push from behind (one who is endeavoring to climb); to push up; hence, to assist in overcoming obstacles, or in making advancement.

As a noun boost is

a push from behind, as to one who is endeavoring to climb; help.

As a verb deepen

is to make deep or deeper.

As a noun depth is

the vertical distance below a surface; the degree to which something is deep.

In intransitive terms the difference between delve and deepen

is that delve is to dig the ground, especially with a shovel while deepen is to become lower in tone.

As a noun delve

is a pit or den.

In intransitive terms the difference between research and deepen

is that research is to make an extensive investigation into while deepen is to become lower in tone.

As verbs the difference between research and deepen

is that research is to search or examine with continued care; to seek diligently while deepen is to make deep or deeper.

As a noun research

is diligent inquiry or examination to seek or revise facts, principles, theories, applications, etc.; laborious or continued search after truth.

As an adverb deeply

is at depth, in a deep way.

As a verb deepen is

to make deep or deeper.

Increase is a related term of deepen.

In lang=en terms the difference between increase and deepen

is that increase is to make (a quantity) larger while deepen is to become lower in tone.

As verbs the difference between increase and deepen

is that increase is (of a quantity) to become larger while deepen is to make deep or deeper.

As a noun increase

is an amount by which a quantity is increased.