Tween

Tween is a word coined independently with several meanings:

Tween 20 is a detergent polysorbate.
J. R. R. Tolkien used it in The Fellowship of the Ring (published in 1954) to cover ages from twenty to thirty-two, the period of adolescence for hobbits, who have longer lifespans than humans and aren't considered adults until age 33.
In popular culture around the start of the 21st century, it has been used to describe children in the pre-teen and teenage years, generally in the age range of 8 to 12 years old (according to the definition of The American Heritage® Dictionary of the English Language, Fourth Edition[1]). One source[2] even references the "tween" years as the period between childhood and adulthood, and describes anyone under the age of 30! (see also twixter).
To add to the age group confusion, in some educational and parenting circles "tweenies", children in their "tweens", are in the transition between toddlerhood and regular childhood, typically in their twos.
In animation, it is used to describe intermediate frames often added by an assistant animator or by computer. See tweening.
Tween is also a web comic by Anthony Furtado. See Tween (webcomic).
In Mark Clifton's Star, Bright (1952) it is a reference to the merely ordinary geniuses.[3]
Tweens is also a possible name given for the 2010s decade, the years from 2010 - 2019. It is combined from the words twenty and teen.