Hardwood
The term "Hardwood" refers to wood from mostly deciduous, broad leaved trees, although some tropical trees may vary from this rule.
On average, hardwood is of higher density than softwood, but there is some overlap between the two groups, as there is considerable range of hardness in both groups.
There are many more hardwood species than softwood, about one hundred times as many.
Some common types of hardwood include:  oak, beech, maple, ash, cherry and walnut.

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Softwood
The term "Softwood" is used to refer to wood from conifer trees.  Some common types of softwood are:  spruce, pine, heart-pine and cedar.

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Hardness
As mentioned above there is a wide range hardness for woods, both hard and soft,
Following are the Janka hardness scale rating for some of the more popular wood floor types.

     Brazilian Walnut                (Ipe)          3680
     Brazilian Teak                   (Cumaru)   3540
     Brazilian Rosewood                              3000
     Brazilian Cherry                (Jatoba)     2350
     Mesquite                                                2345
     Santos Mahogany                                2200
     Hickory / Pecan                                   1820
     Brazilian Maple                                     1500
     Hard Maple                                           1430
     Australian Cypress                              1375
     White Oak                                             1360
     White Ash                                             1320
     American Beech                                  1300
     Northern Red Oak                                1290
     Heart Pine                                            1225
     Black Walnut                                       1010
     Red Cedar                                              900