Needs
Part of speech: adverb
Definition: Of necessity; necessarily; indispensably; often with must, and equivalent to "of need".
Part of speech: noun
Definition: A requirement for something; something needed.
Part of speech: verb
Definition: To have an absolute requirement for.
Example sentence: I think that everybody needs four things in life. Everybody needs something to do regardless of age. Everybody needs someone to love. Everybody needs something to hope for, and, of course, everybody needs someone to believe in.
Necessarily
Part of speech: adverb
Definition: inevitably; of necessity
Example sentence: The over-all point is that new technology will not necessarily replace old technology, but it will date it. By definition. Eventually, it will replace it. But it's like people who had black-and-white TVs when color came out. They eventually decided whether or not the new technology was worth the investment.