Emphasis

An HTML tag used to emphasize text.

Please note that it is more important that copy reads well to humans than any boost you may think you will get by tweaking it for bots. If every occurrence of a keyword on a page is in emphasis that will make the page hard to read, convert poorly, and may look weird to search engines and users alike.

<em>emphasis</em> would appear as emphasis

In FM transmission, the intentional alteration of the amplitude-vs.-frequency characteristics of the signal to reduce adverse effects of noise in a communication system. Note: The high-frequency signal components are emphasized to produce a more equal modulation index for the transmitted frequency spectrum, and therefore a better signal-to-noise ratio for the entire frequency range.