Age-related.

I'm not sure how old I am.

In my research lab, I'm 25. I control numerous things and people and speak with a confidence and maturity I don't always possess. In this atmosphere, I am regarded with intellectual respect. I can analyze and interpret results on the spot, answering questions and pointing out problems to my professor's delight. I walk in and am greeted by name, and people are paid for accommodating my requests.

In Arabic, I'm 5. I pronounce the letters of the alphabet with great care, memorizing what they look like and tracing their exotic shapes. Asking questions correctly and interpreting answers based on context is my game, and like a small child, I smile and nod when correctly understood.

As a program director and TA, I'm 23. Seniors are my students and volunteers, and as their non-PhD reference, I must know everything they know and how to integrate it with the course material I teach. In this context, I must understand and thoroughly answer unclear and misphrased questions, and the things I say are written down to be memorized before an exam.

My birth certificate tells me that last month I turned 19, though I don't feel like the number describes me. Nineteen seems both too old and too young, especially when my age varies so much by situation. I lose credibility when someone I talk to asks about my age before my resume, but gain nearly as much as I lose when someone asks about my accomplishments without realizing my age.

It's an arbitrary concept, really. Age isn't determined by a date on a birth certificate. Age is an emergent illusion that derives from the combination of the way I look, the way I speak, and the way I present myself to a new and judgmental audience.

For two years, my solution has been thus: I present myself as the Generic College-Age Pre-Professional Student, and nobody has to wonder whether the girl at the front of the classroom teaching techniques in immunohistochemical staining is still technically a teenager.