observador
/obseɾbaˈdoɾ/ · B2 · adj
observant
👀🔍 observador = observe + -dor (one who does): the one who watches closely
Spanish observar means to watch, from Latin observare. The suffix -dor marks a doer, like in trabajador (worker). So observador is the one who observes, and as an adjective, someone observant. Sounds close to English observer.