organ or cell able to respond to light, heat, or other external stimulus. A nerve ending that changes stimuli into impulses.

Body of water falling from something tall. To fall, flow, or hang down in a large amount.

raise levels of physiological or nervous activity in.

Made for use by one single person. single human being.

information and skills acquired through experience and education.

fungal growth. Short fungus shaped like an umbrella you can eat. To increase in size or degree suddenly and quickly.

short passage from text, film, etc.. Parts taken from a longer written work. remove.

To keep (machine) working by checking, repairing.

Commercial transactions conducted electronically on the internet..

Concerning one particular thing or kind of thing. medicine or remedy effective in treating particular disease.

Flat, raised structure that people stand on.

mixture of elements. Closed walled areas, as in a prison. To make something from various parts or components.

Used before you explain something simply, clearly.

devotion of time and attention to gaining knowledge of academic subject. Topics or subjects you research or learn about. To focus on learning something usually at school.