learning project might use a single feature, while a more sophisticated machine learning project could use millions of features, specified as {x1,x2,...xN}. What are the Features in spam detector example? • words in the email text • sender's address • time of day the email was sent • email contains the phrase "one weird trick." Labels: A label is the thing we're predicting denoted by y. The label could be the future price of wheat, the kind of animal shown in a picture etc.