Advertisement Upgrade to remove ads


a pattern, plan, representation , or description designed to show the structure or working of an object, system or concept


a set of particles or interacting components considered to be a distinct physical entity for the purpose of study


an explanaiton that is based on prior scientific research or observations and that can be tested

controlled experiment

an experiment that tests only one factor at a time by using a comparison of a control group with an experimental group

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again


Reload the page to try again!


Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording