This is the 2849th most frequent Russian word.
активная
"Active."
Here, 'активная' describes a student's actively engaged behavior during lessons.
Она очень активная ученица, всегда задает интересные вопросы.
She is a very active student; she always asks interesting questions.
In this context, 'активная' is used figuratively to describe an proactive and dynamic approach to life.
Активная жизненная позиция помогает достигать целей.
An active life position helps to achieve goals.
'Активная' here specifies a functional phase of the experiment where there is engagement or participation.