Tween is a word that typically refers to a person who is between the ages of 9 to 12 years old, in grades 4-6. The term is often described in popular media as referring to a pre-adolescent (usually female) who is at the "in-between" stage in their development when they are considered "too old for toys, too young for boys". The "tween" stage usually ends with the onset of puberty, though this may vary.
Tween is a portmanteau of the words teen and between. Tweens are "in-between" being a child and a teen. They would still be children but they share some characteristics of teenagers as they are becoming them, such as, sometimes, changing bodies, growing interest in the opposite gender, etc., and they differ from younger children in that they are not, usually, primarily occupied with play. Although they may appear like teens, abstract thought is almost nonexistent, which makes rebellion as "tweens" rare and they tend to be conformist, especially with the media. They are often going through a period of rapid social, physiological and emotional development. Along with the teen years, the tween years are a time of the most rapid and dramatic change in development since conception and early infancy.
There are currently 20 million tweens in the U.S. and they are projected to hit 23 million by 2020 (U.S. Census). Tweens are a highly diverse segment of the U.S. population. Minorities will comprise more than half of all children by 2023, with nearly 40% projected to be Hispanic.
Literature suggests that when children reach their tween years (8–12 years old), they begin to develop unique social needs and desires, and reveal distinctive hopes, dreams, and expectations for the future. Most notably in this age group, physical changes brought on by the onset of puberty are accompanied by emotional changes. Tweens begin to develop their own sense of self and seek out information from parents, the media, and peers that will help them further define themselves. They are beginning to identify their own interests and express themselves through their activities and the first adult interests start to emerge, such as playing sports, playing musical instruments, cooking, sewing, using computers, etc. Many schools and other organizations encourage tweens to start joining sports, clubs, bands, orchestras, and religious activities. At the same time, tween self-esteem is in development and fragile, at best. As such, tweens are highly affected by peers and face pressures and worries that are often focused on how they will fit in and interact with others in society.
Tweens in marketing 
The word "tweens" is used by marketing firms and advertisers targeting younger demographics, which include tweens and young children. Marketers no longer target kids aged 2–11 as one segment. Instead, they target multiple demographics, some of which overlap:
- infants (Birth-12 months)
- toddlers (1-3)
- young children (3-7)
- children (7-9)
- preteens/tweens (9-12)
- teens (12-18)
- "tween." Dictionary.com, American Heritage Dictionary of the English Language, 4th ed. Houghton Mifflin, 2004. Web. 4 May 2010.
- Aucoin, Don (2 February 2005). "Too old for toys, too young for boys". The Boston Globe. Retrieved 2011-02-04.
- "It's Tween time". Deccan Chronicle. Retrieved 2011-02-04.
- "Tween Talk: Too Old For Toys, Too Young For Boys". Take The Handle. Retrieved 2011-02-04.
- Clifford-Poston, Andrea. Tweens: What to Expect From – and How to Survive – Your Child's Pre-teen Years. Oxford: Oneworld, 2005. Print.
- Jayson, Sharon. "It's Cooler than Ever to Be a Tween, but Is Childhood Lost?" USA Today. 2 February 2009. Web.
- Faw, Larissa. “Tween Spending and Influence.” EPM Communications, Inc. 2008.
- Aeffect, Inc. “Review of Literature to Support Development of the Youth Media Campaign: Exploring How to Motivate Behavior Change Among Tweens in America.” Prepared for CDC. December 2000. Web.