riddle - The circle of two

Inspired by the succes of this puzzle, here is another riddle:

Smaller than the Great Graham!

Smaller than the monster, but also much greater than the monster,

am I equal to two-in-a-circle.

What am I?

Note: If you include the full answer, you will hit the character limit for answers (30000 characters). Please use an abbreviation. Yes, this is a clue.

Answer

You are

Mega

Smaller than the Great Graham!

Smaller than Graham's Number

Smaller than the monster, but also much greater than the monster,

EDIT: 'mega' is the prefix for 1000², 'tera', from the Greek for "monster" (thanks, @wythagoras!), is the prefix for 1000⁴. So a Mega is much greater than tera- anything, lowercase-m mega is smaller than its tera counterpart.

am I equal to two-in-a-circle.

See link for first spoilertag