Pound and ib are essentially the same thing.
Fundamental. Used to emphasize the basic. Intrinsic nature of a person or thing. Relating to the most important characteristics or ideas of something.
Referring to the very core of something. Refers to something’s nature. Used to identify or stress the basic or essential character or nature of a person.
Notice the tie between essentially and the word essence, referring to the very core of something. Used when stating the most basic facts.