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"Dinámicas" is a form of "dinámico", an adjective which is often translated as "dynamic". "Actividades" is a form of "actividad", a noun which is often translated as "activity". Learn more about the difference between "dinámicas" and "actividades" below.
la actividad()
A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
