Hardness can be divided into several categories in terms of metal strength, and some of these categories include yield strength, compressive strength, and tensile strength. In addition to measuring a metal's overall strength, these standards also provide an accurate measure of the quality of the metal itself. A number of metals such as chromium, tungsten, and titanium, which are commonly found in nature, present excellent strength characteristics, but in comparison to man-made metals such as steel and Inconel alloys, they are not as intense as natural metals. In terms of strength, tungsten is rated as the world's strongest metal, which is derived from the Swedish word "heavy stone".